what did rutherford discover from the gold foil experiment

Sciencing_Icons_Science SCIENCE

Sciencing_icons_biology biology, sciencing_icons_cells cells, sciencing_icons_molecular molecular, sciencing_icons_microorganisms microorganisms, sciencing_icons_genetics genetics, sciencing_icons_human body human body, sciencing_icons_ecology ecology, sciencing_icons_chemistry chemistry, sciencing_icons_atomic & molecular structure atomic & molecular structure, sciencing_icons_bonds bonds, sciencing_icons_reactions reactions, sciencing_icons_stoichiometry stoichiometry, sciencing_icons_solutions solutions, sciencing_icons_acids & bases acids & bases, sciencing_icons_thermodynamics thermodynamics, sciencing_icons_organic chemistry organic chemistry, sciencing_icons_physics physics, sciencing_icons_fundamentals-physics fundamentals, sciencing_icons_electronics electronics, sciencing_icons_waves waves, sciencing_icons_energy energy, sciencing_icons_fluid fluid, sciencing_icons_astronomy astronomy, sciencing_icons_geology geology, sciencing_icons_fundamentals-geology fundamentals, sciencing_icons_minerals & rocks minerals & rocks, sciencing_icons_earth scructure earth structure, sciencing_icons_fossils fossils, sciencing_icons_natural disasters natural disasters, sciencing_icons_nature nature, sciencing_icons_ecosystems ecosystems, sciencing_icons_environment environment, sciencing_icons_insects insects, sciencing_icons_plants & mushrooms plants & mushrooms, sciencing_icons_animals animals, sciencing_icons_math math, sciencing_icons_arithmetic arithmetic, sciencing_icons_addition & subtraction addition & subtraction, sciencing_icons_multiplication & division multiplication & division, sciencing_icons_decimals decimals, sciencing_icons_fractions fractions, sciencing_icons_conversions conversions, sciencing_icons_algebra algebra, sciencing_icons_working with units working with units, sciencing_icons_equations & expressions equations & expressions, sciencing_icons_ratios & proportions ratios & proportions, sciencing_icons_inequalities inequalities, sciencing_icons_exponents & logarithms exponents & logarithms, sciencing_icons_factorization factorization, sciencing_icons_functions functions, sciencing_icons_linear equations linear equations, sciencing_icons_graphs graphs, sciencing_icons_quadratics quadratics, sciencing_icons_polynomials polynomials, sciencing_icons_geometry geometry, sciencing_icons_fundamentals-geometry fundamentals, sciencing_icons_cartesian cartesian, sciencing_icons_circles circles, sciencing_icons_solids solids, sciencing_icons_trigonometry trigonometry, sciencing_icons_probability-statistics probability & statistics, sciencing_icons_mean-median-mode mean/median/mode, sciencing_icons_independent-dependent variables independent/dependent variables, sciencing_icons_deviation deviation, sciencing_icons_correlation correlation, sciencing_icons_sampling sampling, sciencing_icons_distributions distributions, sciencing_icons_probability probability, sciencing_icons_calculus calculus, sciencing_icons_differentiation-integration differentiation/integration, sciencing_icons_application application, sciencing_icons_projects projects, sciencing_icons_news news.

• Share Tweet Email Print
• Home ⋅
• Science Fair Project Ideas for Kids, Middle & High School Students ⋅

About Rutherford's Gold Foil Experiment

Five Types of Atomic Models

Ernest Rutherford, originally from New Zealand, is credited as being the father of nuclear physics for his discoveries in atomic structure, even though Hantaro Nagaoka, a physicist from the Imperial University of Tokyo, first proposed the theory of the nucleus as it is known today. Rutherford's "gold foil experiment" led to the discovery that most of an atom's mass is located in a dense region now called the nucleus. Prior to the groundbreaking gold foil experiment, Rutherford was granted the Nobel Prize for other key contributions in the field of chemistry.

The popular theory of atomic structure at the time of Rutherford's experiment was the "plum pudding model." This model was developed in 1904 by J.J. Thompson, the scientist who discovered the electron. This theory held that the negatively charged electrons in an atom were floating in a sea of positive charge--the electrons being akin to plums in a bowl of pudding. Although Dr. Nagaoka had published his competing theory that electrons orbit a positive nucleus, akin to the way the planet Saturn is orbited by its rings, in 1904, the plum pudding model was the prevailing theory on the structure of the atom until it was disproved by Ernest Rutherford in 1911.

The gold foil experiment was conducted under the supervision of Rutherford at the University of Manchester in 1909 by scientist Hans Geiger (whose work eventually led to the development of the Geiger counter) and undergraduate student Ernest Marsden. Rutherford, chair of the Manchester physics department at the time of the experiment, is given primary credit for the experiment, as the theories that resulted are primarily his work. Rutherford's gold foil experiment is also sometimes referred to as the Geiger-Marsden experiment.

The gold foil experiment consisted of a series of tests in which a positively charged helium particle was shot at a very thin layer of gold foil. The expected result was that the positive particles would be moved just a few degrees from their path as they passed through the sea of positive charge proposed in the plum pudding model. The result, however, was that the positive particles were repelled off of the gold foil by nearly 180 degrees in a very small region of the atom, while most of the remaining particles were not deflected at all but rather passed right through the atom.

Significance

The data generated from the gold foil experiment demonstrated that the plum pudding model of the atom was incorrect. The way in which the positive particles bounced off the thin foil indicated that the majority of the mass of an atom was concentrated in one small region. Because the majority of the positive particles continued on their original path unmoved, Rutherford correctly deducted that most of the remainder of the atom was empty space. Rutherford termed his discovery "the central charge," a region later named the nucleus.

Rutherford's discovery of the nucleus and proposed atomic structure was later refined by physicist Niels Bohr in 1913. Bohr's model of the atom, also referred to as the Rutherford Bohr model, is the basic atomic model used today. Rutherford's description of the atom set the foundation for all future atomic models and the development of nuclear physics.

Related Articles

What are the 4 atomic models, what are the different kinds of models of atoms, what contributions did j.j. thomson make to the atom, james chadwick atomic theory, list of the atomic theories, who discovered iodine 131, who discovered the particle theory, cern plans to search for mysterious fifth force particle, who was the african american nuclear scientist who..., how to make a gold atom model, atomic structure of gold, what are an atom, electron, neutron and proton, the locations of protons, neutrons and electrons within..., how to know if an element has a positive or negative..., what are the properties of protons, six elements named after scientists.

Photo Credits

iSailorr/iStock/Getty Images

Find Your Next Great Science Fair Project! GO

• Why Does Water Expand When It Freezes

Gold Foil Experiment

• Faraday Cage
• Oil Drop Experiment
• Magnetic Monopole
• Why Do Fireflies Light Up
• Types of Blood Cells With Their Structure, and Functions
• The Main Parts of a Plant With Their Functions
• Parts of a Flower With Their Structure and Functions
• Parts of a Leaf With Their Structure and Functions
• Why Does Ice Float on Water
• Why Does Oil Float on Water
• How Do Clouds Form
• What Causes Lightning
• How are Diamonds Made
• Types of Meteorites
• Types of Volcanoes
• Types of Rocks

Who did the Gold Foil Experiment?

The gold foil experiment was a pathbreaking work conducted by scientists Hans Geiger and Ernest Marsden under the supervision of Nobel laureate physicist Ernest Rutherford that led to the discovery of the proper structure of an atom . Known as the Geiger-Marsden experiment, it was performed at the Physical Laboratories of the University of Manchester between 1908 and 1913.

The prevalent atomic theory at the time of the research was the plum pudding model that was developed by Lord Kelvin and further improved by J.J. Thomson. According to the theory, an atom was a positively charged sphere with the electrons embedded in it like plums in a Christmas pudding.

With neutrons and protons yet to be discovered, the theory was derived following the classical Newtonian Physics. However, in the absence of experimental proof, this approach lacked proper acceptance by the scientific community.

What is the Gold Foil Experiment?

Description.

The method used by scientists included the following experimental steps and procedure. They bombarded a thin gold foil of thickness approximately 8.6 x 10 -6 cm with a beam of alpha particles in a vacuum. Alpha particles are positively charged particles with a mass of about four times that of a hydrogen atom and are found in radioactive natural substances. They used gold since it is highly malleable, producing sheets that can be only a few atoms thick, thereby ensuring smooth passage of the alpha particles. A circular screen coated with zinc sulfide surrounded the foil. Since the positively charged alpha particles possess mass and move very fast, it was hypothesized that they would penetrate the thin gold foil and land themselves on the screen, producing fluorescence in the part they struck.

Like the plum pudding model, since the positive charge of atoms was evenly distributed and too small as compared to that of the alpha particles, the deflection of the particulate matter was predicted to be less than a small fraction of a degree.

Observation

Though most of the alpha particles behaved as expected, there was a noticeable fraction of particles that got scattered by angles greater than 90 degrees. There were about 1 in every 2000 particles that got scattered by a full 180 degree, i.e., they retraced their path after hitting the gold foil.

Simulation of Rutherford’s Gold Foil Experiment Courtesy: University of Colorado Boulder

The unexpected outcome could have only one explanation – a highly concentrated positive charge at the center of an atom that caused an electrostatic repulsion of the particles strong enough to bounce them back to their source. The particles that got deflected by huge angles passed close to the said concentrated mass. Most of the particles moved undeviated as there was no obstruction to their path, proving that the majority of an atom is empty.

In addition to the above, Rutherford concluded that since the central core could deflect the dense alpha particles, it shows that almost the entire mass of the atom is concentrated there. Rutherford named it the “nucleus” after experimenting with various gases. He also used materials other than gold for the foil, though the gold foil version gained the most popularity.

He further went on to reject the plum pudding model and developed a new atomic structure called the planetary model. In this model, a vastly empty atom holds a tiny nucleus at the center surrounded by a cloud of electrons. As a result of his gold foil experiment, Rutherford’s atomic theory holds good even today.

Rutherford’s Atomic Model

Rutherford’s Gold Foil Experiment Animation

• Rutherford demonstrated his experiment on bombarding thin gold foil with alpha particles contributed immensely to the atomic theory by proposing his nuclear atomic model.
• The nuclear model of the atom consists of a small and dense positively charged interior surrounded by a cloud of electrons.
• The significance and purpose of the gold foil experiment are still prevalent today. The discovery of the nucleus paved the way for further research, unraveling a list of unknown fundamental particles.
• Chemed.chem.purdue.edu
• Chem.libretexts.org
• Large.stanford.edu
• Radioa ctivity.eu.com

Article was last reviewed on Friday, February 3, 2023

Related articles

5 responses to “Gold Foil Experiment”

Super very much helpful to me,clear explanation about every act done by our Rutherford that is under different sub headings ,which is very much clear to ,to study .very much thanks to the science facts.com.thank u so much.

Good explanation,very helpful ,thank u ,so much

very clear and helpful, perfect for my science project!

Thank you for sharing the interactive program on the effects of the type of atom on the experiment! Looking forward to sharing this with my ninth graders!

Rutherford spearheaded with a team of scientist in his experiment of gold foil to capture the particles of the year 1911. It’s the beginning of explaining particles that float and are compacted . Rutherford discovered this atom through countless experiments which was the revolutionary discovery of the atomic nuclear . Rutherford name the atom as a positive charge and the the center is the nucleus.

Barack Hussein Obama

Mrs. Danize Obama

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

Popular Articles

Join our Newsletter

Fill your E-mail Address

Related Worksheets

• Privacy Policy

© 2024 ( Science Facts ). All rights reserved. Reproduction in whole or in part without permission is prohibited.

What is the 'Gold Foil Experiment'? The Geiger-Marsden experiments explained

Physicists got their first look at the structure of the atomic nucleus.

J.J. Thomson model of the atom

Gold foil experiments, rutherford model of the atom.

• The real atomic model

Additional Resources

Bibliography.

The Geiger-Marsden experiment, also called the gold foil experiment or the α-particle scattering experiments, refers to a series of early-20th-century experiments that gave physicists their first view of the structure of the atomic nucleus and the physics underlying the everyday world. It was first proposed by Nobel Prize -winning physicist Ernest Rutherford.

As familiar as terms like electron, proton and neutron are to us now, in the early 1900s, scientists had very little concept of the fundamental particles that made up atoms . 

In fact, until 1897, scientists believed that atoms had no internal structure and believed that they were an indivisible unit of matter. Even the label "atom" gives this impression, given that it's derived from the Greek word "atomos," meaning "indivisible." 

But that year, University of Cambridge physicist Joseph John Thomson discovered the electron and disproved the concept of the atom being unsplittable, according to Britannica . Thomson found that metals emitted negatively charged particles when illuminated with high-frequency light. 

His discovery of electrons also suggested that there were more elements to atomic structure. That's because matter is usually electrically neutral; so if atoms contain negatively charged particles, they must also contain a source of equivalent positive charge to balance out the negative charge.

By 1904, Thomson had suggested a "plum pudding model" of the atom in which an atom comprises a number of negatively charged electrons in a sphere of uniform positive charge,  distributed like blueberries in a muffin. 

The model had serious shortcomings, however — primarily the mysterious nature of this positively charged sphere. One scientist who was skeptical of this model of atoms was Rutherford, who won the Nobel Prize in chemistry for his 1899 discovery of a form of radioactive decay via α-particles — two protons and two neutrons bound together and identical to a helium -4 nucleus, even if the researchers of the time didn't know this.

Rutherford's Nobel-winning discovery of α particles formed the basis of the gold foil experiment, which cast doubt on the plum pudding model. His experiment would probe atomic structure with high-velocity α-particles emitted by a radioactive source. He initially handed off his investigation to two of his protégés, Ernest Marsden and Hans Geiger, according to Britannica . 

Rutherford reasoned that if Thomson's plum pudding model was correct, then when an α-particle hit a thin foil of gold, the particle should pass through with only the tiniest of deflections. This is because α-particles are 7,000 times more massive than the electrons that presumably made up the interior of the atom.

Marsden and Geiger conducted the experiments primarily at the Physical Laboratories of the University of Manchester in the U.K. between 1908 and 1913. 

The duo used a radioactive source of α-particles facing a thin sheet of gold or platinum surrounded by fluorescent screens that glowed when struck by the deflected particles, thus allowing the scientists to measure the angle of deflection. 

The research team calculated that if Thomson's model was correct, the maximum deflection should occur when the α-particle grazed an atom it encountered and thus experienced the maximum transverse electrostatic force. Even in this case, the plum pudding model predicted a maximum deflection angle of just 0.06 degrees. 

Of course, an α-particle passing through an extremely thin gold foil would still encounter about 1,000 atoms, and thus its deflections would be essentially random. Even with this random scattering, the maximum angle of refraction if Thomson's model was correct would be just over half a degree. The chance of an α-particle being reflected back was just 1 in 10^1,000 (1 followed by a thousand zeroes). 

Yet, when Geiger and Marsden conducted their eponymous experiment, they found that in about 2% of cases, the α-particle underwent large deflections. Even more shocking, around 1 in 10,000 α-particles were reflected directly back from the gold foil.

Rutherford explained just how extraordinary this result was, likening it to firing a 15-inch (38 centimeters) shell (projectile) at a sheet of tissue paper and having it bounce back at you, according to Britannica  

Extraordinary though they were, the results of the Geiger-Marsden experiments did not immediately cause a sensation in the physics community. Initially, the data were unnoticed or even ignored, according to the book "Quantum Physics: An Introduction" by J. Manners.

The results did have a profound effect on Rutherford, however, who in 1910 set about determining a model of atomic structure that would supersede Thomson's plum pudding model, Manners wrote in his book.

The Rutherford model of the atom, put forward in 1911, proposed a nucleus, where the majority of the particle's mass was concentrated, according to Britannica . Surrounding this tiny central core were electrons, and the distance at which they orbited determined the size of the atom. The model suggested that most of the atom was empty space.

When the α-particle approaches within 10^-13 meters of the compact nucleus of Rutherford's atomic model, it experiences a repulsive force around a million times more powerful than it would experience in the plum pudding model. This explains the large-angle scatterings seen in the Geiger-Marsden experiments.

Later Geiger-Marsden experiments were also instrumental; the 1913 tests helped determine the upper limits of the size of an atomic nucleus. These experiments revealed that the angle of scattering of the α-particle was proportional to the square of the charge of the atomic nucleus, or Z, according to the book "Quantum Physics of Matter," published in 2000 and edited by Alan Durrant.  

In 1920, James Chadwick used a similar experimental setup to determine the Z value for a number of metals. The British physicist went on to discover the neutron in 1932, delineating it as a separate particle from the proton, the American Physical Society said . 

What did the Rutherford model get right and wrong?

Yet the Rutherford model shared a critical problem with the earlier plum pudding model of the atom: The orbiting electrons in both models should be continuously emitting electromagnetic energy, which would cause them to lose energy and eventually spiral into the nucleus. In fact, the electrons in Rutherford's model should have lasted less than 10^-5 seconds. 

Another problem presented by Rutherford's model is that it doesn't account for the sizes of atoms. 

Despite these failings, the Rutherford model derived from the Geiger-Marsden experiments would become the inspiration for Niels Bohr 's atomic model of hydrogen , for which he won a Nobel Prize in Physics .

Bohr united Rutherford's atomic model with the quantum theories of Max Planck to determine that electrons in an atom can only take discrete energy values, thereby explaining why they remain stable around a nucleus unless emitting or absorbing a photon, or light particle.

Thus, the work of Rutherford, Geiger  (who later became famous for his invention of a radiation detector)  and Marsden helped to form the foundations of both quantum mechanics and particle physics. 

Rutherford's idea of firing a beam at a target was adapted to particle accelerators during the 20th century. Perhaps the ultimate example of this type of experiment is the Large Hadron Collider near Geneva, which accelerates beams of particles to near light speed and slams them together. 

• See a modern reconstruction of the Geiger-Marsden gold foil experiment conducted by BackstageScience and explained by particle physicist Bruce Kennedy . 
• Find out more about the Bohr model of the atom which would eventually replace the Rutherford atomic model. 
• Rutherford's protege Hans Gieger would eventually become famous for the invention of a radioactive detector, the Gieger counter. SciShow explains how they work .

Thomson's Atomic Model , Lumens Chemistry for Non-Majors,.

Rutherford Model, Britannica, https://www.britannica.com/science/Rutherford-model

Alpha particle, U.S NRC, https://www.nrc.gov/reading-rm/basic-ref/glossary/alpha-particle.html

Manners. J., et al, 'Quantum Physics: An Introduction,' Open University, 2008. 

Durrant, A., et al, 'Quantum Physics of Matter,' Open University, 2008

Ernest Rutherford, Britannica , https://www.britannica.com/biography/Ernest-Rutherford

Niels Bohr, The Nobel Prize, https://www.nobelprize.org/prizes/physics/1922/bohr/facts/

House. J. E., 'Origins of Quantum Theory,' Fundamentals of Quantum Mechanics (Third Edition) , 2018

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Robert Lea is a science journalist in the U.K. who specializes in science, space, physics, astronomy, astrophysics, cosmology, quantum mechanics and technology. Rob's articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University

Stephen Hawking's black hole radiation paradox could finally be solved — if black holes aren't what they seem

Physicists unveil 1D gas made of pure light

2,700-year-old shields and helmet from ancient kingdom unearthed at castle in Turkey

Most Popular

• 2 James Webb Telescope goes 'extreme' and spots baby stars at the edge of the Milky Way (image)
• 3 Why can't you suffocate by holding your breath?
• 4 Space photo of the week: Entangled galaxies form cosmic smiley face in new James Webb telescope image
• 5 Did Roman gladiators really fight to the death?

May, 1911: Rutherford and the Discovery of the Atomic Nucleus

In 1909, Ernest Rutherford’s student reported some unexpected results from an experiment Rutherford had assigned him. Rutherford called this news the most incredible event of his life.

In the now well-known experiment, alpha particles were observed to scatter backwards from a gold foil. Rutherford’s explanation, which he published in May 1911, was that the scattering was caused by a hard, dense core at the center of the atom–the nucleus.

Ernest Rutherford was born in New Zealand, in 1871, one of 12 children. Growing up, he often helped out on the family farm, but he was a good student, and received a scholarship to attend the University of New Zealand. After college he won a scholarship in 1894 to become a research student at Cambridge. Upon receiving the news of this scholarship, Rutherford is reported to have said, “That’s the last potato I’ll ever dig.”

At Cambridge, the young Rutherford worked in the Cavendish lab with J.J. Thomson, discoverer of the electron. Rutherford’s talent was quickly recognized, and in 1898 he took a professorship at McGill University in Montreal. There, he identified alpha and beta radiation as two separate types of radiation, and studied some of their properties, though he didn’t know that alphas were helium nuclei. In 1901 Rutherford and chemist Frederick Soddy found that one radioactive element can decay into another. The discovery earned Rutherford the 1908 Nobel Prize in Chemistry, which irritated him somewhat because he considered himself a physicist, not a chemist. (Rutherford is widely quoted as having said, “All science is either physics or stamp collecting”)

In 1907 Rutherford returned to England, to the University of Manchester. In 1909, he and his colleague Hans Geiger were looking for a research project for a student, Ernest Marsden. Rutherford had already been studying the scattering of alpha particles off a gold target, carefully measuring the small forward angles through which most of the particles scattered. Rutherford, who didn’t want to neglect any angle of an experiment, no matter how unpromising, suggested Marsden look to see if any alpha particles actually scattered backwards.

Marsden was not expected to find anything, but nonetheless he dutifully and carefully carried out the experiment. He later wrote that he felt it was a sort of test of his experimental skills. The experiment involved firing alpha particles from a radioactive source at a thin gold foil. Any scattered particles would hit a screen coated with zinc sulfide, which scintillates when hit with charged particles. Marsden was to sit in the darkened room, wait for his eyes to adjust to the darkness, and then patiently stare at the screen, expecting to see nothing at all.

Instead, Marsden saw lots of tiny, fleeting flashes of yellowish light, on average more than one blip per second.

He could hardly believe what he saw. He tested and retested every aspect of the experiment, but when he couldn’t find anything wrong, he reported the results to Rutherford.

Rutherford too was astonished. As he was fond of saying, “It was as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."

About one in every few thousand of the alpha particles fired at the gold target had scattered at an angle greater than 90 degrees. This didn’t fit with the prevailing model of the atom, the so-called plum pudding model developed by J.J. Thomson. In this model electrons were believed to be stuck throughout a blob of positively charged matter, like raisins in a pudding. But this sort of arrangement would only cause small angle scattering, nothing like what Marsden had observed.

After thinking about the problem for over a year, Rutherford came up with an answer. The only explanation, Rutherford suggested in 1911, was that the alpha particles were being scattered by a large amount of positive charge concentrated in a very small space at the center of the gold atom. The electrons in the atom must be orbiting around this central core, like planets around the sun, Rutherford proposed.

Rutherford carried out a fairly simple calculation to find the size of the nucleus, and found it to be only about 1/100,000 the size of the atom. The atom was mostly empty space.

In March 1911, Rutherford announced his surprising finding at a meeting of the Manchester Literary and Philosophical Society, and in May 1911, he published a paper on the results in the Philosophical Magazine .

Later Rutherford and Marsden tried the experiment with other elements as the target, and measured their nuclei as well.

The solar system model was not immediately accepted. One obvious problem was that according to Maxwell’s equations, electrons traveling in a circular orbit should radiate energy, and therefore slow down and fall into the nucleus. A solar system atom wouldn’t last long.

Fortunately, Niels Bohr was soon able to save the solar system model by applying new ideas from quantum mechanics. He showed that the atom could stay intact if electrons were only allowed to occupy certain discrete orbitals.

Though Rutherford still didn’t know what was in this nucleus he had discovered (protons and neutrons would be identified later), his insight in 1911, which overturned the prevailing plum pudding model of the atom, had opened the way for modern nuclear physics.

Ernie Tretkoff

Join your society.

If you embrace scientific discovery, truth and integrity, partnership, inclusion, and lifelong curiosity, this is your professional home.

• Anatomy & Physiology
• Astrophysics
• Earth Science
• Environmental Science
• Organic Chemistry
• Precalculus
• Trigonometry
• English Grammar
• U.S. History
• World History

... and beyond

• Socratic Meta
• Featured Answers

• Rutherford's Gold Foil Experiment

Key Questions

Rutherford's experiment showed that the atom does not contain a uniform distribution of charge.

Explanation:

Thomson's plum pudding model viewed the atom as a massive blob of positive charge dotted with negative charges.

A plum pudding was a Christmas cake studded with raisins ("plums"). So think of the model as a spherical Christmas cake.

When Rutherford shot α particles through gold foil, he found that most of the particles went through. Some scattered in various directions, and a few were even deflected back towards the source.

He argued that the plum pudding model was incorrect. The symmetrical distribution of charge would allow all the α particles to pass through with no deflection.

Rutherford proposed that the atom is mostly empty space. The electrons revolve in circular orbits about a massive positive charge at the centre.

His model explained why most of the α particles passed straight through the foil. The small positive nucleus would deflect the few particles that came close.

The nuclear model replaced the plum pudding model. The atom now consisted of a positive nucleus with negative electrons in circular orbits around it .

Rutherford arrived in Manchester in the summer of 1907, months before the university's term began. He had been named Langworthy Professor of Physics, successor to Arthur Schuster (1851–1934), who retired at age 56 to recruit Rutherford. Schuster had built a modern physics building, hired Hans Geiger, Ph.D. (1882–1945) because of his experimental skill, and endowed a new position in mathematical physics to round out a full physics program. Rutherford entered the center of the physics world. Researchers came to him by the dozen.

You need Flash Player installed to listen to this audio clip.

I found Rutherford's place very busy, hard working. But a very dirty place. Namely, Manchester is very foggy, foggy and smoky. And of course everywhere you see smoke there, everywhere the smoke. Now the technique used in Rutherford’s lab was to fit up an electroscope. You have to build it yourself of cocoa boxes, gold leaf and sulfur isolation. And you charge the electroscope by sealing wax which you rubbed on your trousers. So it was a very primitive technique. But of course also a microscope to read the electroscope. Now the microscope was fixed and then you were not supposed to touch it. And of course you were not supposed to clean it. So years went on without apparatus being cleaned. But apart from the shortcomings it was a very fine lab, nice rooms, and lots of people working there—able people.... I remember Moseley very well, with whom I was on very friendly terms. I will tell you later about his work. And Charles Darwin was there. He was lecturing in theoretical physics. And Russell, who later came to Oxford. An Italian, Rossi, did spectroscopic work. He showed that ionium and sodium have the same spectrum. And then Geiger was there. He was an assistant. And also an assistant named Makower, who died since. Geiger and Makower published a book together. And also a chap Robinson, who worked on beta rays. Gray, a New Zealand man. Marsden who came from Australia. Fajans who came from Germany. And Boltwood was there for a while. He came from Yale. Rutherford invited him in hope that Boltwood, a great chemist, would purify ionium, but he failed as many others.

Rutherford arrived with many research questions in mind. He was not done with the puzzles of the decay families of thorium, radium, etc., but he was passing much of this work to Boltwood, Hahn, and Soddy. Boltwood and Hahn both worked with Rutherford in Manchester, Boltwood in 1909–1910 and Hahn in 1907–1908. Rutherford was gradually turning his attention much more to the α (alpha), β (beta), and γ (gamma) rays themselves and to what they might reveal about the atom. That is, he was leaving radio-chemistry to others and turning to physics.

Rutherford's early team at Manchester included Geiger and William Kay (1879–1961), junior laboratory assistant since 1894. Rutherford promoted Kay to laboratory steward in 1908, to manage lab equipment and to aid him in his research. In 1957, Kay thought back to his youth with Rutherford in an interview. The language is quaint, but the description is as close to Rutherford's approach as we get. The questioner was Samuel Devons (1914–2006), who was one of Rutherford's last students in the 1930s.

[Devons] “When you were here [in Manchester], during this period... did Rutherford actually make any apparatus himself?” [Kay] “No, no, no, no. We used to, I used to set up nearly all his apparatus. You know, when he did his work, you know, oftener than not, he used to tell me and we did a rough experiment, re...” [D.] “Did he sketch out what he wanted?” [K.] “Well, he'd tell you what he wanted, roughly, you see, but he'd let you make what you wanted, you see, he'd tell you what he was going to do, which was very good, you see. It gives you......... it learnt you a lot and you knew what to do and what not to do. And then we would do a rough experiment, and get one or two curves you see, and then straight away button it on to somebody else to do the real work, and that's how he did his........ attacked these little things, you see.” [D.] “He tried them out himself first?” [K.] “He'd try a rough experiment himself on the little things, d'you see, and then he'd turn it over on to somebody...” (Quoted in Hughes, p. 104)

Rutherford and Hans Geiger worked closely in 1907 and 1908 on the detection and measurement of α particles. If they were to use α particles to probe the atom, they had first to know more about these particles and their behavior. Rutherford had tried and failed back at McGill to count α particles.

A year later in Manchester, he and Geiger succeeded with two methods of observing α particles. The first method involved scintillations excited by α particles on a thin layer of zinc sulfide. They observed these through a microscope and counted the scintillations at different angles of dispersion. They also developed an "electrometer" that could demonstrate the passage of an individual α particle to a large audience. The instrument, which evolved into the "Geiger counter," had a partially evacuated metal cylinder with a wire down its center. They applied a voltage between the cylinder and the wire high enough almost to spark. They admitted α particles through a thin mica window, where these particles collided with gasses, producing gas ions. These then collided with other molecules and produced more ions, and so on. Each α particle produced a cascade of ions, which partially discharged the cylinder and indicated the passage of an α particle. Geiger and Rutherford published several articles in 1908 and 1909 on these methods and their use.

Rutherford wrote to Henry Bumstead (1870–1920), an American physicist, on 11 July 1908:

Geiger is a good man and worked like a slave. I could never have found time for the drudgery before we got things going in good style. Finally all went well, but the scattering is the devil. Our tube worked like a charm and we could easily get a throw of 50 mm. for each particle. ... Geiger is a demon at the work of counting scintillations and could count at intervals for a whole night without disturbing his equanimity. I damned vigorously and retired after two minutes. (Quoted in Eve, p. 180.)

Although Rutherford suspected as early as 1906 that α particles were helium atoms stripped of their electrons, he demanded a high standard of proof. One kind of experiment was not enough. One kind of detector was not enough. He wanted more proof. For this, Rutherford desired "big voltages" and big electromagnets to divert α particles, but this method was not yet ripe. Lab steward William Kay recalled in the cited oral history interview that Rutherford in 1908 insisted that strong electric and magnetic fields were needed to measure more directly the charge and mass of the α and β particles:

And that's what he was after all the time. That's what he got at Cambridge [after 1919], which we never got here, you see, because we'd got no money. (Hughes, “William Kay,” 2008, pp. 109–110.)

Kay said Rutherford wanted a big, water-cooled magnet, but that he “dropped it like a hot cake” when he learned its cost. So he needed a new line of attack. The new line was very simple, a chemical procedure mixed with physics. For this work Rutherford recruited Thomas Royds (1884–1955), who had earned his Physics Honours degree in 1906. They collected α particles in a sealed glass tube, compressed them, and passed an electric spark through. They studied the emitted light in a spectroscope and found it to be identical to the spectrum of helium. Within a few months, Rutherford was awarded the Nobel Prize for Chemistry, "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances." (Nobel citation) Rutherford and Royds had established the identity and primary properties of α particles. Rutherford next turned his attention to using them to probe the atom.

The autumn of 1908 began an important series of researches. Geiger had been passing beams of α particles through gold and other metallic foils, using the new detection techniques to measure how much these beams were dispersed by the atoms in the foils. Geiger thought Ernest Marsden (1889–1970), a 19-year-old student in Honours Physics, was ready to help on these experiments and suggested it to Rutherford. Since Rutherford often pushed third-year students into research, saying this was the best way to learn about physics, he readily agreed.

Geiger and Marsden began with small-angle dispersion and tried various thicknesses of foils, seeking mathematical relationships between dispersion and thickness of foil or number of atoms traversed. Marsden later recalled that Rutherford said to him amidst these experiments: "See if you can get some effect of alpha-particles directly reflected from a metal surface." (Reported by Marsden in Birks, 1962, p. 8). Marsden doubted that Rutherford expected back scatter of α particles, but as Marsden wrote

...it was one of those 'hunches' that perhaps some effect might be observed, and that in any case that neighbouring territory of this Tom Tiddler's ground might be explored by reconnaissance. Rutherford was ever ready to meet the unexpected and exploit it, where favourable, but he also knew when to stop on such excursions. (Birks, 1962, p. 8)

This was Rutherford's playful approach in action. His students and others tried out his ideas, many of which were dead-ends. This idea to look for backscattering of α particles, however, paid off. Rutherford wrote:

Experiment, directed by the disciplined imagination either of an individual or, still better, of a group of individuals of varied mental outlook, is able to achieve results which far transcend the imagination alone of the greatest philosopher. (Quoted in Eve, 1939, Frontmatter)

Sometime later in 1908 or 1909, Marsden said, he reported his results to Rutherford. Rutherford recalled this a little differently:

I remember ...later Geiger coming to me in great excitement and saying, 'We have been able to get some of the α -particles coming backwards...' It was quite the most incredible event that has ever happened to me in my life. It was almost incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. ( Rutherford , 1938, p. 68)

Human memory is fallible. Whether Marsden or Geiger told Rutherford, the effect was the same. Rutherford said they should prepare a publication from this research, which they submitted in May 1909. Moreover, this started Rutherford thinking toward what ultimately, almost two years later, he published as a theory of the atom.

What was Rutherford doing for the rest of 1909 and all of 1910? For one thing, his close friend Boltwood was in Manchester for the academic year working with Rutherford on radioactive decay products of radium. He was also reviewing and speaking on earlier ideas about atomic structure. Most importantly, he was taking the phenomenon of the scattering of α particles apart systematically and testing each piece. Rutherford did not have his bold idea — the nuclear atom — instantly, but he came to it gradually by considering the problem from many sides.

In the autumn of 1910 he brought Marsden back to Manchester to complete rigorous experimental testing of his ideas with Geiger. They re-established rates of emission and the ranges of α particles by radioactive sources and they re-examined their statistical analyses. Rutherford tried to reconcile scattering results with different atomic models, especially that of J.J. Thomson, in which the positive electricity was considered as dispersed evenly throughout the whole sphere of the atom.

At some point in the winter of 1910–1911, Rutherford worked out the basic idea of an atom with a "charged center." As Geiger and Marsden pointed out in their 1909 article:

If the high velocity and mass of the α -particle be taken into account, it seems surprising that some of the α -particles, as the experiment shows, can be turned within a layer of 6 x 10 -5 cm. of gold through an angle of 90°, and even more. To produce a similar effect by a magnetic field, the enormous field of 109 absolute units would be required. (Birks, p. 179)

Rutherford concluded in his May 1911 paper that such a remarkable deviation in the path of a massive charged particle could only be achieved if most of the mass of, say, an atom of gold and most of its charge were concentrated in a very small central body. Note: at this point in 1911, Rutherford did not call this a "nucleus."

The first public announcement of the nuclear theory by Rutherford was made at a meeting of the Manchester Literary and Philosophical Society, and he invited us young boys to go to the meeting. He said he’d got some interesting things to say and he thought we’d like to hear them. We didn’t know what it was about at that time. The older people in the laboratory did, of course Geiger and Marsden knew because they were already doing the experiments. In fact, unless they had done some which were sufficient to be decisive, Rutherford never mentioned it publicly. And, of course, Darwin knew about it much earlier. But that must have been early in 1911, and we went to the meeting and he told us. And he mentioned then that there was some experimental evidence which had been obtained by Geiger and Marsden. He did not, as far as I remember, say more about the results than that they were quite decisive. And, as I said before, he would never have made a public announcement of that kind if he hadn’t had good evidence. And that is one of the characteristics that runs through all Rutherford’s work, particularly all his work up to the end of the Manchester period. If you look at some of his papers in the early days — I call McGill the early days — he was quite convinced that the alpha particles were atoms of helium, but he never said that in those words. He always said they were either atoms of helium or molecules of hydrogen or perhaps he may have said something else of that weight. It was quite characteristic of him that he would never say a thing was so unless he had experimental evidence for it that really satisfied him.

In fact, Rutherford was exceedingly cautious in drawing conclusions about this central charge: “A simple calculation shows that the atom must be a seat of an intense electric field in order to produce such a large deflexion at a single encounter.” (Birks, p. 183). He worked out quickly and roughly that several quantitative relationships should be true if this basic theory were correct. First, the number of α particles scattered through a given angle should be proportional to the thickness of the foil. Second, that number should be proportional to the square of the nuclear charge. Lastly, it should be inversely proportional to the fourth power of the velocity of the α particle. These three ideas laid out the experimental program of Geiger and Marsden for the next year.

Rutherford’s interest was then almost entirely in the research. He had done very little teaching in McGill. He was research professor. I suppose he gave some lectures but it would have been very few. And his interest was quite naturally on the research side. He did give some lectures, but elementary lectures, the kind of thing you would expect a man to know before he came to the University. They were the lectures to the engineers. They were a rowdy lot and Rutherford could keep them under control. There was perhaps only one other man in the department who could have done it, and he (Rutherford?) enjoyed them because he was able to show them the very interesting experiments one can perform in elementary courses.

It's often been said to me that Rutherford was a bad lecturer. I never heard such nonsense. It is quite true that on occasion he would be a bit dull, a bit mixed up, but that was only on very rare occasions. There were other occasions when he was really most stimulating. There was a tremendous enthusiasm about him.

Rutherford entertained the possibility that the charged center is negative. That sounds odd today, so what made it reasonable? First, it wasn't very different from Thomson's model. Second, since Rutherford knew that α particles carry a double + charge, he thought this might act the same way the Sun does on a comet sweeping near it. It would slingshot the α particle around and back towards its source. He also considered a nearly forgotten model suggested by Japanese physicist Hantaro Nagaoka (1865–1950) — the Saturnian model. Nagaoka and Rutherford were in contact in 1910 and 1911 and Rutherford mentioned Nagaoka's model of "a central attracting mass surround by rings of rotating electrons" (Birks, p. 203). The end result in this critical Rutherford paper, however, was Rutherford's announcement that whether the atom were a disk or a sphere, and indeed whether the central charge were positive or negative, would not affect the calculations. Rutherford was always careful not to claim more than his results could support.

Rutherford did see possible tests of the nature of the central charge. The absorption of β particles, he said, should be different with a negative center versus a positive one. A positive center would explain the great velocity that α particles achieve during emission from radioactive elements. But these were only hints.

Geiger and Marsden did indeed work systematically through the testable implications of Rutherford's central charge hypothesis. The first major publication of their results was in German in the Proceedings of the Vienna Academy of Sciences ( Sitzungberichte der Wiener Akademie der Wissenschaften) in 1912. This 30-page version was followed by one in English in 1913 in the Philosophical Magazine: "The Laws of Deflexion of α Particles through Large Angles" The English version is the better known. Slight differences between the two led one historian to suggest that Rutherford decided in favor of a positively charged center by August 1912 (Trenn, 1974). Rutherford's other team members, especially Charles Galton Darwin (1887–1962), H.G.J. Moseley (1887–1915), and Niels Bohr (1885–1962) figured prominently in the ultimate establishment of Rutherford's nuclear atom.

The ‘Great War’ totally disrupted work in Rutherford's Manchester department. Bohr returned to Denmark. Marsden accepted a professorship in New Zealand. Moseley died in the Battle of Gallipoli. James Chadwick (1891–1974), who was working with Geiger at the Technical University of Berlin when war broke out, spent several years interned in the Ruhleben camp for prisoners of war. Other students went off to war, too, and Rutherford devoted considerable energy to mobilizing science for the war effort and specifically to anti-submarine techniques.

Against this distracted background, Rutherford and his lab steward, William Kay, began in 1917 to explore the passage of α particles through hydrogen, nitrogen, and other gases. When the Great War ended, Ernest Marsden briefly helped with the tedious scintillation observations that provided clues to the nature of the nucleus. Rutherford reported the tentative results of these extensive experiments in 1919. Rutherford placed a source of radium C (bismuth-214) in a sealable brass container, fitted so that the position of the source could be changed and so that different gases could be introduced or a vacuum produced, as desired. The α particles traversed the interior of the container and passed through a slit, covered by a silver plate or other material, and hit a zinc sulfide screen, where a scintillation was observed in a darkened room. When hydrogen gas was introduced into the container and care was taken to absorb the α particles before they hit the screen, scintillations were still observed. Rutherford posited that as the α particles traversed the hydrogen gas, they occasionally collided with hydrogen nuclei. As Rutherford wrote, this produced “swift hydrogen atoms” which were mostly projected forward in the direction of the α particles’ original motion.

Rutherford had several subtle questions in mind during these experiments, mostly concerned with the nature of the nucleus. He asked his colleague Darwin to analyze these collisions based on a ‘simple theory’ of elastic collisions between point nuclei repelled according to an inverse square law, the α particles carrying a charge of 2 times that of an electron (and of opposite sign) and the hydrogen nuclei 1 times. Darwin found that all α particles approaching within 2.4x10 -13 cm would produce a ‘swift hydrogen atom.’ This simple theory, however, predicted far fewer accelerated hydrogen atoms than were observed in the experiments.

Rutherford rejected explanations of this variance based on different charges on the particles or other laws than inverse square laws. Rather, he concluded that for distances on the order of the diameter of the electron, ‘the structure of the helium nucleus can no longer be regarded as a point…’. He posited that the helium nucleus ( α particle) has a complex structure of four hydrogen nuclei plus two negatively charged electrons. (We would say it is composed of two protons.) Rutherford concluded that deformation of complex nuclei during collisions was a more likely explanation, the variation of the forces between the nuclei varying in a complex way on close approach.

Taking into account the intense forces brought into play in such collisions, it would not be surprising if the helium nucleus were to break up. No evidence of such a disintegration…has been observed, indicating that the helium nucleus must be a very stable structure.

We must remember that Rutherford could not directly observe the structure of the nucleus, so his conclusions were tentative. Nevertheless, he was openly considering the possibilities of a complex nucleus, capable of deformation and even of possible disintegration. These thoughts shaped this intense period of experimental researches.

Home | Sections | Credits | Exhibit Hall | About Us

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center
• What is the model of the atom proposed by Ernest Rutherford?
• What were the results of Rutherford's experiment?
• What did Ernest Rutherford's atomic model get right and wrong?
• What was the impact of Ernest Rutherford's theory?
• When did science begin?
• Where was science invented?
• Is mathematics a physical science?
• Why does physics work in SI units?

What is the Rutherford gold-foil experiment?

A piece of gold foil was hit with alpha particles , which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. Some particles had their paths bent at large angles. A few even bounced backward. The only way this would happen was if the atom had a small, heavy region of positive charge inside it.

Related Questions

Experimental Evidence for the Structure of the Atom

George sivulka march 23, 2017, submitted as coursework for ph241 , stanford university, winter 2017, introduction.

The Rutherford Gold Foil Experiment offered the first experimental evidence that led to the discovery of the nucleus of the atom as a small, dense, and positively charged atomic core. Also known as the Geiger-Marsden Experiments, the discovery actually involved a series of experiments performed by Hans Geiger and Ernest Marsden under Ernest Rutherford. With Geiger and Marsden's experimental evidence, Rutherford deduced a model of the atom, discovering the atomic nucleus. His "Rutherford Model", outlining a tiny positively charged atomic center surrounded by orbiting electrons, was a pivotal scientific discovery revealing the structure of the atoms that comprise all the matter in the universe.

The experimental evidence behind the discovery involved the scattering of a particle beam after passing through a thin gold foil obstruction. The particles used for the experiment - alpha particles - are positive, dense, and can be emitted by a radioactive source. Ernest Rutherford discovered the alpha particle as a positive radioactive emission in 1899, and deduced its charge and mass properties in 1913 by analyzing the charge it induced in the air around it. [1] As these alpha particles have a significant positive charge, any significant potential interference would have to be caused by a large concentration of electrostatic force somewhere in the structure of the atom. [2]

Previous Model of the Atom

The scattering of an alpha particle beam should have been impossible according to the accepted model of the atom at the time. This model, outlined by Lord Kelvin and expanded upon by J. J. Thompson following his discovery of the electron, held that atoms were comprised of a sphere of positive electric charge dotted by the presence of negatively charged electrons. [3] Describing an atomic model similar to "plum pudding," it was assumed that electrons were distributed throughout this positive charge field, like plums distributed in the dessert. However, this plum pudding model lacked the presence of any significant concentration of electromagnetic force that could tangibly affect any alpha particles passing through atoms. As such, alpha particles should show no signs of scattering when passing through thin matter. [4] (see Fig. 2)

The Geiger Marsden Experiments

Testing this accepted theory, Hans Geiger and Ernest Marsden discovered that atoms indeed scattered alpha particles, a experimental result completely contrary to Thompson's model of the atom. In 1908, the first paper of the series of experiments was published, outlining the apparatus used to determine this scattering and the scattering results at small angles. Geiger constructed a two meter long glass tube, capped off on one end by radium source of alpha particles and on the other end by a phosphorescent screen that emitted light when hit by a particle. (see Fig. 3) Alpha particles traveled down the length of the tube, through a slit in the middle and hit the screen detector, producing scintillations of light that marked their point of incidence. Geiger noted that "in a good vacuum, hardly and scintillations were observed outside of the geometric image of the slit, "while when the slit was covered by gold leaf, the area of the observed scintillations was much broader and "the difference in distribution could be noted with the naked eye." [5]

On Rutherford's request, Geiger and Marsden continued to test for scattering at larger angles and under different experimental parameters, collecting the data that enabled Rutherford to further his own conclusions about the nature of the nucleus. By 1909, Geiger and Marsden showed the reflection of alpha particles at angles greater than 90 degrees by angling the alpha particle source towards a foil sheet reflector that then would theoretically reflect incident particles at the detection screen. Separating the particle source and the detector screen by a lead barrier to reduce stray emission, they noted that 1 in every 8000 alpha particles indeed reflected at the obtuse angles required by the reflection of metal sheet and onto the screen on the other side. [6] Moreover, in 1910, Geiger improved the design of his first vacuum tube experiment, making it easier to measure deflection distance, vary foil types and thicknesses, and adjust the alpha particle stream' velocity with mica and aluminum obstructions. Here he discovered that both thicker foil and foils made of elements of increased atomic weight resulted in an increased most probable scattering angle. Additionally, he confirmed that the probability for an angle of reflection greater than 90 degrees was "vanishingly small" and noted that increased particle velocity decreased the most probably scattering angle. [7]

Rutherford's Atom

Backed by this experimental evidence, Rutherford outlined his model of the atom's structure, reasoning that as atoms clearly scattered incident alpha particles, the structure contained a much larger electrostatic force than earlier anticipated; as large angle scattering was a rare occurrence, the electrostatic charge source was only contained within a fraction of the total volume of the atom. As he concludes this reasoning with the "simplest explanation" in his 1911 paper, the "atom contains a central charge distributed through a very small volume" and "the large single deflexions are due to the central charge as a whole." In fact, he mathematically modeled the scattering patterns predicted by this model with this small central "nucleus" to be a point charge. Geiger and Marsden later experimentally verified each of the relationships predicted in Rutherford's mathematical model with techniques and scattering apparatuses that improved upon their prior work, confirming Rutherford's atomic structure. [4, 8, 9] (see Fig. 1)

With the experimentally analyzed nature of deflection of alpha rays by thin gold foil, the truth outlining the structure of the atom falls into place. Though later slightly corrected by Quantum Mechanics effects, the understanding of the structure of the the atom today almost entirely follows form Rutherford's conclusions on the Geiger and Marsden experiments. This landmark discovery fundamentally furthered all fields of science, forever changing mankind's understanding of the world around us.

© George Sivulka. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.

[1] E. Rutherford, "Uranium Radiation and the Electrical Conduction Produced By It," Philos. Mag. 47 , 109 (1899).

[2] E. Rutherford, "The Structure of the Atom," Philos. Mag. 27 , 488 (1914).

[3] J. J. Thomson, "On the Structure of the Atom: an Investigation of the Stability and Periods of Oscillation of a Number of Corpuscles Arranged at Equal Intervals Around the Circumference of a Circle; with Application of the Results to the Theory of Atomic Structure," Philos. Mag. 7 , 237 (1904).

[4] E. Rutherford, "The Scattering of α and β Particles by Matter and the Structure of the Atom," Philos. Mag. 21 , 669 (1911).

[5] H. Geiger, "On the Scattering of the α Particles by Matter," Proc. R. Soc. A 81 , 174 (1908).

[6] H. Geiger and E. Marsden, "On a Diffuse Reflection of the α-Particles," Proc. R. Soc. A 82 , 495 (1909).

[7] H. Geiger, "The Scattering of the α Particles by Matter," Proc. R. Soc. A 83 , 492 (1910).

[8] E. Rutherford, "The Origin of α and β Rays From Radioactive Substances," Philos. Mag. 24 , 453 (1912).

[9] H. Geiger and E. Marsden, "The Laws of Deflexion of α Particles Through Large Angles," Philos. Mag. 25 , 604 (1913).

• Fundamentals NEW

• Biographies
• Compare Countries
• World Atlas

To share with more than one person, separate addresses with a comma

• Privacy Notice
• Terms of Use

Stack Exchange Network

Stack Exchange network consists of 183 Q&A communities including Stack Overflow , the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Why Rutherford used only gold foil in his famous gold foil experiment?

why didn't Rutherford use an aluminium foil, or a silver foil. Why he used gold foil in his gold foil experiment?

• atomic-physics

• 1 $\begingroup$ That's really a question you need to ask from Geiger and Marsden: en.wikipedia.org/wiki/Geiger%E2%80%93Marsden_experiment . It might have something to do with the fact that gold can be hammered into extremely thin foils, which is not possible (as far as I know) with either aluminum or silver. That reason is also given in the Wikipedia article. $\endgroup$ –  CuriousOne Commented Jun 5, 2016 at 10:01

4 Answers 4

He actually used also Aluminium, Silver, and Copper. He did so because he wanted to prove that the Rutherford cross section was proportional to $Z^2$.

In any case, he needed to use malleable material (metals) in order to achieve a micrometer-thin foil to prevent the entire $\alpha$ beam to be absorbed by the target.

• $\begingroup$ Hey this looks like a fantastic answer; can you give a citation for it? $\endgroup$ –  Selene Routley Commented Jun 5, 2016 at 12:55
• $\begingroup$ Professor Longo said it during the Nuclear Physics course at Sapienza university. The material used are cited also on Wikipedia's article: en.wikipedia.org/wiki/Geiger –Marsden_experiment I had forgotten one element:he used tin, too. $\endgroup$ –  Drebin J. Commented Jun 5, 2016 at 13:12

Is this true?

In a 1913 paper, The Laws of Deflexion of α Particles through Large Angles... Geiger and Marsden reused the above apparatus to measure how the scattering pattern varied with the square of the nuclear charge (i.e. if s ∝ Qn2). Geiger and Marsden didn't know what the positive charge of the nucleus of their metals were (they had only just discovered the nucleus existed at all), but they assumed it was proportional to the atomic weight, so they tested whether the scattering was proportional to the atomic weight squared. Geiger and Marsden covered the holes of the disc with foils of gold, tin, silver, copper, and aluminum. They measured each foil's stopping power by equating it to an equivalent thickness of air. They counted the number of scintillations per minute that each foil produced on the screen.

See Wikipedia

Yes, it is correct that Rutherford used other metallic atoms instead of gold. From using other metallic atoms, he drew the following conclusion that there shall be no change in his prior observations, if and only if the malleability of the metal is sufficive enough for the alpha particles to penetrate through, otherwise there shall be a lack of penetration of the alpha particles, thus different scattering of particles, which would ultimately for-go his previous experiment.

Geiger and Marsden first used Gold because it is a malleable metal and they could relatively easily produce foils of a thickness of around $1\; \mu$m which still is about 3500 atoms thick. Even so this was thin enough to observe an incoming alpha particle interacting with only one nucleus and not being absorbed by the foil.

Other malleable metals were then used to see what effect they had on the scattering of alpha particle. The parameter which they used to categorise a metal was its atomic weight as mentioned by @Mikhail in his question and they did find that the scattering was approximately proportional to the atomic weight squared.

It was Moseley who first systematically associated atomic number $Z$ with the number of positive charges in the nucleus.

Your Answer

Sign up or log in, post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged atomic-physics radiation scattering or ask your own question .

• Featured on Meta
• User activation: Learnings and opportunities
• Preventing unauthorized automated access to the network

Hot Network Questions

• Why aren't some "conditions" officially a condition? (Burning, Bloodied)
• Can I stack deck floor frames on top of each other?
• Firefox isn't upgraded on Debian: its ESR has 1.5 years old, ensuring it being discarded. How to ask a global upgrade from Debian or Mozilla team?
• What made scientists think that chemistry is reducible to physics and when did that happen?
• What kind of Fibonacci subword at this offset?
• Enhancing my RSA implement in Python
• How close are aircraft allowed to get to each other mid-flight?
• How to adjust the water amount when soaking rice before cooking?
• Compact category which is not idempotent complete
• What is synthetic flywheel mass?
• Could you suffocate someone to death with a big enough standing wave?
• How can one be compensated for loss caused negligently by someone who dies in the process?
• Why should an attacker perform a clickjacking attack when he can simulate the click with JavaScript?
• How to Use the Function from @AlainMatthes (https://tex.stackexchange.com/a/58735/278762) with 50 Teeth?
• Could a Project like Orion be built today with non nuclear weapons?
• Should punctuation (comma, period, etc.) be placed before or after the inches symbol when listing heights?
• Musicians wearing Headphones
• Why can’t acceleration in GR be defined the same way as in EM?
• In the absence of an agreement addressing the issue, is there any law giving a university copyright in an undergraduate student's class paper?
• How do I link a heading containing spaces in Markdown?
• Finite two-relator groups and quotients of knot groups
• Batch Apex: Why is Salesforce giving me an "Internal Salesforce.com Error" when I try to execute a batchable inner class?
• Why doesn't SpaceX use a normal blast trench like Saturn V?
• If I was ever deported, would it only be to my country of citizenship? Or can I arrange something else?