Rutherford Gold Foil Experiment - Online Tutor, Practice Problems & Exam Prep

The Rutherford Gold Foil Experiment, also known as the Geiger-Marsden Experiment, was a groundbreaking study that revolutionized our understanding of atomic structure. Conducted by Ernest Rutherford with the assistance of Hans Geiger and Ernest Marsden, the experiment involved bombarding a thin sheet of gold foil with alpha particles from a radioactive element, typically iridium, encased in a lead box. The alpha particles, consisting of two protons and two neutrons (symbolized as:

${\frac{4}{2}}^{+}\mathrm{He}$

), were expected to pass through the foil. However, some particles were deflected, and a few even rebounded, indicating the presence of a dense, positively charged nucleus at the center of the atom. This led to the dismissal of the Thomson's plum pudding model, which posited that electrons were evenly dispersed in a "soup" of positive charge, and established the nuclear model of the atom. Rutherford's findings revealed that the nucleus, though tiny, contained most of the atom's mass and was orbited by a cloud of electrons, fundamentally altering the field of chemistry and our understanding of atomic theory.

Rutherford Gold Foil Oil Experiment

In 1911, Ernest Rutherford's gold foil experiment led to the discovery of the positively charged nucleus within an atom. Now he was assisted by fellow chemists Hans Geiger and Ernest Marsden, and because they had such a big role in this experiment, it is sometimes also referred to as the Geiger Marsden experiment. OK, so just remember that this experiment is given by both of these names, the Rutherford Gold experiment as well as the Geiger Marsden experiment.

Now the experimental setup is a thin sheet of gold foil. So here we have our gold foil right here is bombarded with alpha particles emitting from a radioactive element. Now, the alpha particle itself, it's a radioactive particle consisting of two protons and two neutrons. So if we were to write out its elemental symbol, All right, so we're going to say it has two protons, which means its atomic number is 2. Its mass number is a number of neutrons and protons together, so that'd be a total of four. And we'd use the alpha symbol. Here, we're not talking about any electrons involved. Neutrons are neutral, protons are positive, so the overall charge would be two plus.

Now we'd say that an element on the periodic table also has an atomic number of two, and that would be helium. So another way of depicting this alpha particle is 42, helium 2 plus. Now we're going to say here that the radioactive element is encased within this lead box with one part of it open, which emits the alpha particles. Now the radioactive element itself is usually Iridium, and again, it's encased within this lead container. Now we're going to say here that around this gold foil or gold sheet, we're going to have what's called our detecting screen. So which is this screen right here? And it has a small slit which allows for the passage of the alpha particles to enter.

Now what happens here is that the alpha particles are emitted from the Iridium, and what we saw is that some of the alpha particles would go through the gold foil and they would hit the back of the detecting screen. But we also found that some of these positively charged alpha particles would be striking something in the center of our gold foil. This would cause some of these alpha particles to change trajectories. They wouldn't go straight through it. That would hit different parts of the detecting sheet, would surprise our chemists, and in some cases the alpha particle would shoot out towards the gold foil and come right back towards the radioactive source.

Now from this we were able to come up with well, Rutherford was able to come up with his three postulates, and the postulates were one that the proton and neutron are located in the nucleus which lies at the center of the atom. And Rutherford was also able to determine that, although incredibly small, the nucleus comprised most of the mass of the atom. And then finally Rutherford was able to figure out that surrounding the dense positively charged nucleus is a cloud of electrons.

So from the gold foil experiment we're able to come up with these three postulates in the case of Rutherford and his assistants. Now these are seen as common known ideas today, but back then it was pretty groundbreaking and went against a lot of at the time laws, at least people chemist considered them to be laws. So this kind of turned all that on top of its head and kind of challenged a lot of the conceptions that chemists had at that time. OK, so through the actions of Rutherford and Geiger and Marsden, we have a better understanding of the atom.

Rutherford Gold Foil Oil Experiment Example 1

In this example question, it says the goldfoil Rutherford used in his experiment had a thickness of approximately 6.0×10-3mm. If a single gold atom has a diameter of 2.9×10-8cm, how many atoms thick was Rutherford's foil? All right, so here we need to determine what is our end amount. Here they want us to determine the amount of atoms. So the number of atoms will be our end amount, and our given amount is just the value that possesses only one unit connected to it.

Within this question, we have two values being given here. They're saying that we have 60×10-3mm. And in this other value, it's actually not alone, it's actually a conversion factor. It's telling US1 atom has this value. So the conversion factor is 1 atom is 2.9×10-8cm. Remember we're going to start with our given amount, which is just a value alone that is not connected to another unit. So we have 6.0×10-3mm that is our given amount.

Remember, we use conversion factors to go from our given amount to our end amount and realize here that if I can convert these millimeters into centimeters, they can cancel out with these centimeters and in that way we can isolate atoms at the end. So that is the approach we're going to take. So our first conversion factor is just going to be converting millimeters to meters. Remember the coefficient of one goes on the side with the metric prefix, meaning one milli is 10-3mm.

Can't slop Now I have meters for conversion factor 2. Now I'm going to go from meters to centimeters. One centi is 10-2. Now that I have centimeters, I can now bring in my conversion factor from the question itself, which is conversion factor 3, so 2.9×10-8cm per one atom. So here centimeters cancel out and I'll have atoms at the end. Make sure you put this in parentheses in your calculator, otherwise you make it the incorrect answer.

And remember, we do that every time we have times 1020 power. If you do that correctly, you'll get as your final answer 2.1×104 atoms. So we would have 2×104 atoms in terms of another atoms involved in the thickness of Rutherford's foil.

Rutherford Gold Foil Oil Experiment

Now through the use of the Rutherford gold foil experiment we are able to develop a new model for the atom itself. We coin it the nuclear model. Now before Rutherford's nuclear model we had Thompson's Plum pudding model. Now with the plum pudding model it was believed that the atom itself had dispersed around it electrons. So these negatively charged electrons were dispersed evenly throughout the atom.

Now to counterbalance these electrons, we actually had positive charges embedded within the atom. This overall gave the atom a neutral charge. Now if this were true, when Rutherford used his alpha particles, they should have all shot through the atom. However, we saw that some of the alpha particles were being deflected from something near the center of the atom itself. This helped to create the nuclear model.

So with the nuclear model and the ejection of alpha particles from our lead container towards the atom, we saw that some of the alpha particles were deflecting back as we fired alpha particles towards them. Now of course some of them did go through because they wouldn't interact with the nucleus itself. But just realize because of the gold foil experiment, Rutherford was able to put to rest this plum pudding model first theorized by Thompson and give us this more accurate nuclear model.

Rutherford Gold Foil Oil Experiment Example 2

In this example, it says Rutherford's experiment with alpha particles scattering by gold foil established that A electrons are positively charged subatomic particles. Even if we didn't know anything about Rutherford's experiment, we should know that this statement is false. Electrons are not positively charged subatomic particles, they're negatively charged subatomic particles. Besides, it improve this, It just proved that at the center of the atom rested A positively charged portion, and we know that portion is the nucleus.

Next, atoms are composed of protons, neutrons and electrons. Now yes, the atom is composed of the subatomic particles. Yes, electrons do orbit the nucleus. Rutherford knew that the nucleus itself were positive, but he wouldn't have known that there were neutrons embedded in it as well, because remember, neutrons possess no charge. There'd be no way of him knowing that they existed within the nucleus as well. So this is not true.

Protons are not evenly distributed throughout an atom. Now here this is true. Protons are not distributed evenly throughout an atom. Like Thompson's plum pudding model would have suggested. The gold foil experiment proved that at the center of the atom itself is where we have a concentration of those protons, so this would be the most accurate.

Finally, protons are about 1000 times lighter than electrons. This is also true. We know that the subatomic particles neutrons are the heaviest, followed by protons and then electrons would be the lightest. Also, if the center wore highly densed as we believed, we'd expect the protons to be much more heavy than the electrons themselves. So here only option C would be the correct choice.

Here’s what students ask on this topic:

What did the gold foil experiment prove?

The gold foil experiment, conducted by Ernest Rutherford in 1909, dramatically changed our understanding of atomic structure. Prior to this experiment, the prevailing model was J.J. Thomson's "plum pudding" model, which suggested that electrons were scattered within a diffuse cloud of positive charge.

Rutherford's experiment involved directing a beam of alpha particles (helium nuclei) at a thin sheet of gold foil. He observed that while most of the alpha particles passed straight through the foil, a small number were deflected at large angles, and some even bounced back toward the source.

The surprising results proved that the plum pudding model was incorrect. Instead, Rutherford proposed a new model where the atom consists of a small, dense nucleus containing most of the atom's mass and all of its positive charge. The electrons were thought to orbit this nucleus, much like planets orbit the sun. This nuclear model of the atom laid the foundation for modern atomic physics and quantum mechanics, and it introduced the concept of a nucleus being the central core of an atom.

Who did the gold foil experiment?

The gold foil experiment, also known as the Geiger-Marsden experiment, was conducted by Ernest Rutherford in 1909, with the assistance of his colleagues Hans Geiger and Ernest Marsden. This groundbreaking experiment was designed to explore the structure of the atom. Rutherford and his team directed a beam of alpha particles at a thin sheet of gold foil and observed the scattering of the particles using a fluorescent screen.

To their surprise, while most of the alpha particles passed through the foil with little or no deflection, a small number were deflected at large angles, and some even bounced back toward the source. This led Rutherford to conclude that the atom's positive charge and most of its mass were concentrated in a small, dense region he called the nucleus, with the electrons orbiting around it, much like planets around the sun. This nuclear model of the atom was a significant departure from the plum pudding model proposed by J.J. Thomson and fundamentally changed our understanding of atomic structure.

What was the gold foil experiment?

The gold foil experiment, also known as the Rutherford gold foil experiment, was a groundbreaking experiment conducted by Ernest Rutherford in 1909. It involved firing a beam of alpha particles (which are helium nuclei) at a thin sheet of gold foil. Rutherford, along with his assistants Hans Geiger and Ernest Marsden, observed the scattering of the alpha particles after they hit the gold foil.

The expectation, based on the then-popular "plum pudding" model of the atom proposed by J.J. Thomson, was that the alpha particles would pass through the foil with minimal deflection. However, while most particles did pass straight through, some were deflected at large angles, and a few even bounced back toward the source.

Rutherford concluded from these unexpected results that the atom must have a small, dense nucleus containing most of its mass and all of its positive charge, with the electrons orbiting around this nucleus. This led to the development of the nuclear model of the atom, fundamentally changing our understanding of atomic structure.