Which of the following represents the correct order of increasing first ionization enthalpy for Ca, Ba, S , Se and Ar ?

Options

A. `Ca lt S lt Ba lt Se lt Ar`
B. `S lt Se lt Ca lt Ba lt Ar`
C. `Ba lt Ca lt Se lt S lt Ar`
D. `Ca lt Ba lt S lt Se lt Ar`

Answer

C

Explanation

Order of increasing `Delta H_(IE_(1)): Ba lt Ca lt Se lt S lt Ar`
`Ba lt Ca , Se lt S`: : On moving top to bottom in a group, size increases. So ionisation energy decreases. Ar : Maximum value of ionisation energy, since it is an inert gas.