Explain why the second ionization energy of B is significantly higher than the second ionization energy of C,

Question

(a) Explain why the second ionization energy of B is significantly higher than the second ionization energy of C, even though the first ionization energy of B is less than C.

(b) Which has higher 1st ionization energy B or Be and why?

Answer 1

B(5) 1s² 2s² 2p¹ C(6) 1s² 2s² 2p²; B after losing one electron, has completely filled s-orbital from which removal of second electron is more difficult than carbon. 

(b) Be has higher first ionization energy due to completely filled valence s-orbital.