# How do you calculate ionization energy using Rydberg constant?

##### 1 Answer

#### Explanation:

The Rydberg equation for absorption is

Where

We are calculating ionisation energy so the electron goes to infinity with respect to the atom, ie it leaves the atom. Hence we set

Assuming we ionise from the ground state, we set

When we deal with such small energies, it is often helpful to work in electron volts.