Bohr model of the atom

Particles have a characteristic wavelength such that

```Q = particle momentum
W = particle wavelength
h = Planck's constant
= 6.62*10^-34 Joule seconds

Q W = h              de Broglie formula
```
Suppose an electron orbits a proton (a hydrogen atom). According to the Bohr theory, the number of wavelengths experienced by the electron during one orbit is an integer.
```R = Orbit radius
C = Orbit circumference
```
The Bohr assumption:
```C = N W                  where N is an integer

N = 1   corresponds to the S orbital
N = 2   corresponds to the P orbital
N = 3   corresponds to the D orbital

M = Electron mass
= 9.11*10^-31 kg
V = Electron velocity
Q = Electron momentum
= M V
e = Electron charge
= -1.60*10^-19 Coulombs
p = Proton charge
= +1.60*10^-19 Coulombs
k = Coulomb constant
= 9.0*10^9  Newtons meters^2 / Coulombs^2
Fe= Electric force
= k p e / R^2
Fc= Centripetal force
= M V^2 / R
```
For an electron in a circular orbit,
```Fe = Fc
```
This sets the characteristic size of the hydrogen atom.
```E = Electric potential energy
= k p e / R
= Energy required to steal the electron from the proton (the "ionization energy").
```