Question

Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also. 

(i) TlCl₃, TlCl (ii) AlCl₃ , AlCl (iii) InCl₃, InCl

Answer 1

(i) TlCl is more stable. It is an ionic compound. Inert pair effect is maximum in thallium and therefore, +1 oxidation state is more stable than +3 state. 

(ii) AlCl₃ is more stable. Anhydrous state is covalent while aqueous state is ionic in nature. +3 oxidation state is more stable than +1 oxidation state. Inert pair effect is negligible. 

(iii) lnCl₃ is more stable. Anhydrous state is more covalent less ionic in nature. Inert pair effect is considerable but less than in thallium.