Chemical Bonding Questions

Which one of the following has a square planar geometry?

In which of the following ionization processes, the bond order has increased and the magnetic behaviour has changed?

Which of the following hydrogen bonds is the strongest?

Which of the following species exhibits diamagnetic behaviour?

The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizing power of the cationic species, ${\text{K}}^{+},{\text{Ca}}^{2+},{\text{Mg}}^{2+},{\text{Be}}^{2+}$?