Hey everyone, welcome to section four of our notes. Today we are going to move into objective number three now and kind of partly number two but not really and we're going to start looking at Niels Bohr. And so we'll scroll down. So Niels Bohr, he was another scientist that worked with the atom just like everyone else who looked at Thompson and Rutherford. And he based his model of the atom off of Rutherford's experiment. So that was in 2.3. And remember Rutherford said that the atom was mostly empty space and that the the nucleus was positive and that the electrons were negative from Thompson's experiments. So this all layers really well. And what Niels Bohr saw was that electrons could have different energy levels and he saw this when he looked at different colors of light. And we're not going to really get into the specifics of this but he came up with the model of the atom that looked like a big like a target. And so he in the middle of his atom, he had a very dense nucleus. So we'll start with this. This is our nucleus. And this nucleus was then surrounded by electrons. So he'd have one row run-ring of electrons and then outside that there would be another ring of electrons. And outside that there would be another ring of electrons. And this goes on and on. And we're going to be talking about what this really means. But here's what Niels Bohr saw. He saw that if an electron started at the first energy level or the first shell, he could energize that electron and get it to bounce up into the second shell. And we can do that a lot of different ways. We can add electricity. We can add energy through heat or by adding light or something like that in some cases. And so when these electrons jump from one shell to another, they are absorbing energy. So to jump means we have to absorb energy. Okay, remember, energy is constant. If I cannot create any energy and I can't destroy any energy, kind of like, you know, can't create a destroy any matter. When this electron then falls back to its original place, it doesn't like to be highly energized. When it falls back, we see something peculiar. We usually get light. That extra energy is released. So the fall after jump, you have to fall. This is the release. We're releasing energy. And this light can be measured. There is a distinct amount of energy between shell one and shell two. So if you had another electron that jumped from shell one, let's say we jump up to three and then fall back down, we get more light. And this light has a higher energy, which is really, really important. And what this led to is being able to develop a way to keep track of these electrons and where they are in the atom because there's rules about how many we can have. So this led to a few things. First of all, your atomic radius or the size of your atom is based on a couple of things. First, the number of protons and neutrons. Because that determines the size of your nucleus. And it's also based on the number of electrons. The more electrons we have, the more energy shells we need and the larger our atom becomes.