Question

Arrange the following in the order of increasing ionization potential
A. `Mg lt A1 lt Si lt P`
B. `A1 lt Si lt P lt Mg`
C. `Si lt P lt Mg lt A1`
D. `A1 lt Mg lt Si lt P`

Answer 1

Correct Answer - D
These elements are members of the `3rd` period. In general ionization potential increases across the period on account of the increase of nuclear charged. But `A1 `had unusually low ionization potential relative to `Mg` as the electron ionized in `A1` is `3p^(1)` while in `Mg`, it is `3s^(2)`. For a given value of `n`, the case of removel of electron is
`s gt p gt dgt f`
The correct order of ionization enthalpy is
`A1 (577 kJ mol^(-1))lt Mg (738) lt Si (786) lt P (1012)`