Question

Why there is a drop ionisation energy at boron and oxygen ?​

Answer 1

Answer:

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.