Ionization Energy:

Definition:

"The energy required to remove the first outermost electron is called the first ionization energy. The energy required to remove the outermost electron from a monovalent positive ion is called the second ionization energy and so on. The higher the ionization and third ionization energies are always larger than the first. The higher the ionization energy, the more difficult it is to remove an electron. It is measured in KJ/mole or ev/atom.

KJ=Kilo Joule and e.v. = electron volt

Dependence of Ionization Energy:

1. Nuclear Charge: The larger the nuclear charge, the greater the I.E.
2. Shielding Effect: The greater the shielding effect, the less the I.E.
3. Radius: The greater the distance between the nucleus and outermost electrons, the less the I.E.
4. Sub-levels: Electrons in the P sub-level have a lower I.E. than a sub-level electrons.

Group Trends in I.E.

I.E. decreases down the group from top to bottom.

Periodic Trends in I.E.

I.E. increases going across a group from left to right.