Ionization Energy

Ionization energy is the energy required to remove an electron from an isolated gaseous atom or ion.

• In simpler terms, it measures how much energy is needed to remove an electron from an atom.

High ionization energy = Difficult to remove an electron.

Low ionization energy = Easier to remove an electron.

First ionization energy is the energy required to remove the first electron from a neutral gaseous atom.

• First ionization energy = Removes the first electron.

• The atom becomes a +1 ion.

Successive Ionization Energies

Successive ionization energies are the energies required to remove additional electrons from an already positively charged ion.

Ionization energy generally decreases down a group.

Why?

1. Atomic radius increases as you move down a group.

2. More electron shells are added.

3. Shielding effect increases.

4. The outermost electron experiences less effective attraction from the nucleus.

5. Less energy is needed to remove it.