Question

In a group from top to bottom, ionisation energy:

• A. decreases
• B. increases
• C. constant
• D. none of these

Answer 1

The correct option is A decreases

In a group atomic size increases down the group as the valence shell increases.I.P is the amount of energy required to remove an electron from the valence shell in it's gaseous state.Hence I.P will be less for the atom which have larger size because no need to give lot of energy to remove electron as effective nuclear charge is less on electrons.Hence I.P in a group decreases.