Question

Arrange the elements S, P, As in order of increasing ionization enthalpy.

• A. $S<P<As$
• B. $P<S<As$
• C. $As<S<P$
• D. $As<P<S$

Answer 1

The correct option is C $As<S<P$

The increasing order of ionization enthalpy is $As<S<P$.
On moving from left to right in a period, the ionization energy increases with few irregularities where half filled and completely filled orbitals are involved.
On moving down the group, the ionization energy decreases.
Hence, the ionization enthalpy of As is lowest.
The ionization energy of P is higher than the ionization energy of S as in P, the electron is to be removed from half filled 3p orbital whereas in case of S, the electron is to be removed from 3p orbital containing 4 electrons.