# How do you calculate the Ionization energy of Hydrogen?

##### 1 Answer

See the explanation that follows...

#### Explanation:

You are able to calculate the ionization energy of hydrogen because of a formula developed by Neils Bohr in his early quantum atom.

Besides his one postulate that limited a characteristic of the electron known as angular momentum, he used mostly classical mechanics to obtain a formula for the allowed energies of the hydrogen atom as

where

was obtained by inserting a number of physical constants that included the mass and charge of the electron.

So, with the electron in the ground state (lowest energy), the value of

If the electron were to be removed from the atom, this corresponded to raising it past all possible values of

To determine the ionization energy, one had only to determine the difference between these two states: