Question

Why is the ionisation energy of beryllium greater than that of hi?

Answer 1

The first ionization of Beryllium is greater than that of Boron because beryllium has a stable complete electronic configuration(1s2 2s2)so it requires more energy to remove the first electron from it......whereas boron has the electronic configuration(1s2 2s2 3s1)which needs lesser energy than that of beryllium to remove the valence electron.

Answer 2

The ionisation energy of Boron is less than that of Beryllium because in Boron there is a complete 2s orbital. The increased shielding of the 2s orbital reduces the ionisation energy. Similarly, the I.E. of Oxygen is less than that of Nitrogen because the extra electron is shielded by the half-filled 2p orbital.