Electropositive character

(i) Electropositive character increases from B to Tl.

(ii) Boron is semi metal, more closer to non-metallic nature whereas rest all members are pure metals.

(iii) Furthermore, these elements are less electropositive than s-block elements because of smaller size and higher ionisation energies.

Oxidation potential

(i) The standard oxidation potentials of these element are quite high and are given below,

B Al Ga In Tl

E⁰op for M ® M³⁺+ 3e – +1.66 +0.56 +0.34 +1.26

E⁰op for M ® M⁺ + e – +0.55 – +0.18 +0.34

(ii) However Boron does not form positive ions in aqueous solution and has very low oxidation potential.

(iii) The higher values of standard oxidation potentials are due to higher heats of hydration on account of smaller size of trivalent cations.

(iv) Aluminium is a strong reducing agent and can reduce oxides which are not reduced even by carbon. This is due to lower ionisation energy of aluminium than carbon. The reducing character of these elements is Al > Ga > In > Tl