Atom and nucleus of atom

Electron orbit
m v^2 / r = e^2 / (4 π ε0 r^2)

The second postulate of Bohr
h ν = E_k - E_n

Quantization of electron orbits
m v r = n h / (2 π)

Bohr orbit radius
r = 4 π ε0 * n^2 * ℏ / (m e^2)

Bohr radius of the electron orbit
r = n^2 * 0,528 * 10^(-10)

Velocity of an electron in a Bohr orbit
v  = saknis(e^2 / (4 π ε0 m r))

Velocity of an electron in a Bohr orbit
v  = e^2 / (4 π ε0 n ℏ)