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's sometimes also referred to as the Geiger Marsden experiment. Okay, 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 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. Alright, so we're going to say it has two protons, which means that the atomic number is two. Its mass number is a number of neutrons and protons together. That'd be a total of four. And would use the alpha symbol here. We're not talking about any electrons involved, neutrons are neutral, protons are positive. So the overall charge will 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 4/2 helium two 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 awful particles. Now the radioactive element itself is usually Iridium and again, it's in case 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 slip 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 off of 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. They 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 postures and the apostle, it's 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 mask of the And then finally Rutherford was able to figure out that surrounding the dense poverty charged nucleus is a cloud of electrons. So from the gold foil experiment were 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 chemists consider them to be lost. So this kind of turned all that on top of its head and kind of challenge a lot of the conceptions that chemists had at that time. Okay, so through the actions of Rutherford and Geiger and Marsden, we have a better understanding of the atom.