Arrange the following elements in the order of incresing first ionizarion enthalpy: `Na, Mg, A1`, and `Si`

Options

A. `Na lt Mglt A1 lt Si`
B. `Na lt Mg lt Silt A1`
C. `Na lt A1 lt Mg lt Si`
D. `Na gt Mg gt A1 gt Si`

Answer

C

Explanation

First ionization enthalpies generally increase from left to right in the same period, but there are anomalies at groups `13` and `16`. All these elements are members of the `3rd` period and `A1` is a group `13` element with only one electron in its outer `p` orbital `(1s^(2)2s^(2)2p^(6)3s^(2)3p^(1))`. Therefore, there is a slight dip at `A1`.