Which of the following is incorrect about group `13` elements?

Options

A. They are less electropositive (or metallic) as compared to `s`-block elements.
B. On moving down the group, the electropositive character increases.
C. The standard reduction electrode potentials `E^(@) (M^(3+)//M)` become less negative from `Al` to `Ga` to `In` and the potential becomes positive for `Tl`.
D. None of these.

Answer

B

Explanation

The electropositive (or metallic) nature of group `13` elements increases from `B` to `Al`, but then decreases from `Al` to `Tl`. The increase in metallic character from `B` to `Al` is the usual trend on descending a group and is associated with the increase of atomic size leading to the decrease of ionization enthalpy. However, `Ga, In`, and `Tl` do not continue the trend. These elements exhibit decreasing tendency to lose electrons because of the poor shielding of valence electrons by the `d`- and `f`-electrons present in the inner shells of these elements.