Ionization Energy Examples

Atoms and molecules have a measurement called the ionization energy, which simply means the amount of energy required to remove one electron while that substance is in a gaseous state. This term used to be called the ionization potential, but that's no longer used. This IE is always measured starting with an outer shell, moving inward towards the nucleus.

Interestingly, as electrons are removed from an atom, it becomes harder to remove more electrons and requires more ionization energy since the charge of the atom has now changed.

There are different units used for measuring IE, depending on which field of science is involved. In physics, the IE is measured in electron volts (eV) and refers to moving a single electron. In chemistry, however, IE is measured as the molar quantity, which is specified as units of kJ/mol or kcal/mol. That's the amount of energy it takes for all the atoms in one mole of a substance to each lose one electron.

1. Hydrogen (H) - 13.6

2. Helium (He) - 24.59

3. Boron (B) - 8.3

4. Carbon (C) - 11.26

5. Nitrogen (N) - 14.53

6. Oxygen (O) - 13.62

7. Sodium (Na) - 5.14

8. Aluminum (Al) - 5.99

9. Chlorine (Cl) - 12.97

10. Calcium (Ca) - 6.11

All of these values, however, are for the first ionization level only. That means that in order to find out the next level's IE, multiply each element's first level ionization energy by 96.4689. Keep multiplying the new values by that number for each corresponding IE.