Chemistry- ionization and other stuff?

Question

I need to know the correct answer to this question to help study for an exam.

1. Explain each of the following observations using principles of atomic structure and/or bonding.
a.) Potassium has a lower first ionization energy than lithium.
b.) The ionic radius of the Nitrogen ion is larger than the oxide ion.
c.) A calcium atom is larger than a zinc atom.
d.) Boron has a lower first ionization energy than beryllium.

Thanks a lot for helping! I will give best answer..

Answer 1

a. bigger radius - outer electron less strongly held
b. one less proton - more repulsions
c. poor screening by d-electrons
d. 2p easier to remove than 2s - screened by 2s.