UPSEE 2017 Solved Paper

In general :
(i) First ionisation energy (I.E ‌1 ) or enthalpy, increases along the period from left to right, but due to half-field configuration of P -atom, it has higher I.E ‌1 than of S-atom.
(ii) IE1 decreases as we move down the group from top to bottom.
(iii) More be the size of atom, less be the IE1. Hence, correct order of IE1 is B<S<P<F.
IE1 for (in kJmol−1 )
B=800
S=999.4
P=1012
F=1680.8