Question

Define ionisation enthalpy and explain the variation of it in the periods and group.

Answer 1

the change in enthalpy to remove an electron from an gaseous isolated atom is called ionisation enthalpy.when we go from left to right in a period the ionisation enthalpy decreases due to the increase in radius.as we go down a group the ionisation enthalpy increases because the effective nuclear charge increase.

Answer 2

The amount of energy required to remove the most loosely bounded electron from the last shell of an isolated gaseous atom is know as Ionisation Enthalpy
Ionisation Enthalpy increases across a period and decreases down a group