Therefore, it was not controversial to quantize the energy which quantized the position of the electron.

Note that he did not assume that the nucleus only had one proton, so that his theories would work for hydrogen and for helium + (helium missing one electron) or Li ++ (lithium missing two electrons) ectetera.īohr knew from reading the debates and talks from the 1911 Solvay Conference that, at this time, quantum mechanics consisted of following the physics rules for almost everything but then adding a quantum twist so that, say, the energy was quantized. He also wanted to derive Balmer’s formula from basic principles, and hydrogen only has one electron. Part 3: Why Did Bohr Make These Assumptions?īohr started with a single electron moving in a circle because he wanted to be as simple as possible. the energy binding the electron to the atom) equals an integer times Planck’s constant times the frequency of the electron’s spin divided by 2! The work needed to remove the electron (i.e. The position of the electron is limited because its energy is quantized with the rule that.All Classical laws of physics apply with three exceptions: 1) he knew that in classical physics objects just don’t jump between positions, 2) in classical physics a rotating charged particle will radiate energy and spiral into the nucleus but Bohr just basically said, “not for my electrons” and 3) in classical physics vibrating electrons create light due to their vibrations, in this theory the light created is due to the change in energy!.The energy of light produced is equal to the change in energy of the electron as it jumps between states.The electron can only circle around the nucleus at set positions, which Bohr called “stationary states” although it can “magically” jump between the rings in a quantum leap (Bohr did not use the word magic).The Electron spins around a nucleus in a stable orbit which assumed to be a circle.In his first paper he only dealt with systems with one electron.1) Tiny Backstory which I just did 2) Bohr’s assumptions, 3) why Bohr made his assumptions, and 4) the math 5) Conclusions for Hydrogen and Helium + !īohr made 6 assumptions in his July, 1913 paper I am going to split this video into 5 parts. So, let me explain how he accomplished this. ” He also found that his new formula could be used to explain strange shadows in a star to being from ionized helium. Niels Bohr was attempting to mesh these two ideas when he was reminded of the equation for the possible frequencies of light produced by burning hydrogen, called the Balmer formula and, as he recalled years later, “as soon as I saw Balmer’s formula, the whole thing was immediately clear to me. Rutherford didn’t know and wasn’t particularly concerned about it. Rutherford didn’t know what that meant about the electrons, maybe they were evenly distributed in the atom, maybe they were in a big ring around the atom like Saturn, maybe they were in many rings. 11 years later Ernest Rutherford had a theory that the majority of an atom is smushed into a tiny nucleus which was assumed to be positive to counter the electrons which are negative. I often use the word quantize, which is defined as “to restrict (a variable quantity) to discrete values rather than to a continuous set of values.” This whole idea of restricting things to discrete values started in 1900 when Max Planck restricted the energy of light to be in little energy packets where the energy equaled a constant (h) times the frequency of light (given the Greek letter v). Ready? Let’s go!īefore I start, I would like to give a tiny backstory. I just made a video about the personal history of Niels Bohr and how he made his model and when I was done, I was asked to make a video showing mathematically in detail how Bohr derived the position, energy, and, most importantly, the frequency of light created for an electron in an atom.

Helium bohr model