Arrange the elements N, P, O and S in the order of - (i) increasing first ionisation enthalpy. (ii) increasing non metallic character. Give reason for the arrangement assigned.

Arrange the elements N, P, O and S in the order of - (i) increasing f

1.	Arrange the elements N, P, O and S in the order of - (i) increasing first ionisation enthalpy. (ii) increasing non metallic character. Give reason for the arrangement assigned.
Answer» Solution :The placing of elements are as Ionisation enthalpy of nitrogen `(""_(7)N=1s^(2),2s^(2),2p^(3))` is greater than oxygen `(.::_(8)O=1s^(2),2s^(2),2p^(4))` DUE to extra stable exactly half-filled 2p-orbitals. Similarly, ionisation enthalpy of phosphorus `(""_(15)P=1s^(2),2s^(2),2p^(6),3S^(2),3P^(3))` is greater than sulphur `(""_(16)S=1s^(2),2s^(2),2p^(6),3s^(2),4p^(4))` On moving down the group, ionisation enthalpy decreases with increasing atomic size.So the ORDER is `S lt P lt O lt N to` first ionisation enthalpy increases. (ii) Non-metallic character across a period (left to right) increases but on moving down the group it decreases. So, the order is, `P lt S ltN lt O to ` Non-metallic character increases.