The increasing order of the first ionisation enthalpies of the elements`B,P,S` and `F` (lowest first) is:

Options

A. `B lt P lt S lt F`
B. `P lt S lt B lt F`
C. `F lt Slt P lt B`
D. `B lt S lt P lt F`

Answer

D

Explanation

In general, the ionization enthalpy increases on moving across the period on account of increase of `Z_(eff)` but decreases down the group on account of increase of atomic size.
`{:(13,14,15,16,17),(B,,,,F),(,,P,S,):}`
But `P` has relatively higher value due to the extra stability of exactly half-full `p` subshell. Thus, the correct order of `Delta_(i)H_(1)` is `B(801kJ mol^(-1))lt S (1000kJ mol^(-)) lt P (1012kJ mol^(-1)) lt F (1680 k J mol^(-))`