Question

Why is the first ionization energy of boron LESS than that of beryllium? Boron has a higher atomic number.

Answer 1

Consider electronic configurations of `Be` versus `B`. Should a `p` electron be easier to remove?

Explanation:

`Be, Z=4, 1s^(2)2s^2.`

`B, Z=5, 1s^(2)2s^(2)2p^1.`

A priori , should it be easier to remove a `p-`orbital electron, which by definition has zero electron density at the nucleus? An `s-`orbital electron, even those of the `2s` shell has some probability density at or near the nucleus, and this probably accounts for the differential ionization energies.