Question

Why nitrogen do not form pentahalides but Phosphorus does?

Answer 1

Electronic configuration of nitrogen is 1s2 2s2 2p3 . Nitrogen use its 2p electrons to form compounds like NCl3 . As Nitrogen is a 2nd period element thus it does not have any vacant d orbital to promote the 2s electrones to get 5 unpaired electron to make a pentahalide . Thus nitrogen does not form any pentavalent compound . But in case of Phosphorus it is an 3rd period elemenet an have a vacant 3d orbital so it can easily promote its 3s electron to this 3d orbital and get 5 unpaired electrons and forms pentahalide