The amount of energy required to liberate the most loosely, bonded electrons from the outer most shell of an element is called as ionisation enregy.
a) Which are the major factors that ionisation energy depends on?
How does ionisation energy vary in groups and periods. Give reason.

Explanation

a) Nuclear charge and size of an atom
b) On moving down a group ionisation energy decreases as the size of the atom increases.
c) As the nuclear charge increases from left to right across a period, ionisation energy increases.