Pairs would form an ionic bond

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.

Ibelieve the answer is weathering,hope my answer has you : ) 

H tricky one let me think and get back to u