a. Explain why the second ionisation energy of `B` is significantly higher than the second ionisation energy of `C`, even though the first ionisation energy of `B` is less than `C`.
b. which has higher `1st` ionisation energy `B` or `Be` and why?

Explanation

`B(5) 1s^(2)2S^(2)2p^(1), " "C(6) 1s^(2)2s^(2)2p^(2)` , B after losing electron , has completely filled s-orbital from which removal of second electron is more difficult than carbon.