Question 1

What is the general valence-shell configuration of Group 13 elements?

Accepted Answer

Group 13 elements have the general valence-shell configuration ns²np¹. This gives each neutral atom three valence electrons: a pair in the s subshell and one electron in a p subshell.

Question 2

Why does anhydrous aluminium chloride form an Al₂Cl₆ dimer?

Accepted Answer

An AlCl₃ unit has an incomplete electron arrangement around aluminium. Two AlCl₃ units associate so that two chlorine atoms form coordinate bonds towards the other aluminium atom, producing dimeric Al₂Cl₆ with two bridging chlorines.

Question 3

What is the ground-state electronic configuration of aluminium?

Accepted Answer

Aluminium has the configuration [Ne] 3s² 3p¹. Its three valence electrons are arranged as a 3s pair and one 3p electron.

Question 4

Why does aluminium have a +3 oxidation state commonly?

Accepted Answer

Aluminium can formally lose its three valence electrons, giving the +3 oxidation state. Group 13 elements can also show +1, formed by losing the np¹ electron and retaining the ns² pair.

Question 5

How does atomic radius change across Group 13?

Accepted Answer

The general trend is B < Al > Ga < In < Tl. Radius increases from B to Al, but poor shielding by Ga d-electrons makes Ga smaller than Al; it then increases through In and Tl.

Question 6

What is the inert-pair effect in Group 13?

Accepted Answer

The inert-pair effect is the increasing tendency of the ns² electron pair, especially the 6s² pair in thallium, to remain non-bonding. Consequently, the +1 state becomes more stable than the +3 state toward the lower part of the group.

Aluminium and Group 13 — Electronic Configuration and Trends

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