Thallium(I) iodide and thallium(III) iodide differ in a subtle way: TlI 3 is actually thallium(I) triiodide rather than thallium(III) iodide. This is best explained by the fact that:

Tl 3+ is much more stable than Tl + and cannot oxidise iodide ions in dilute solution

Thallium does not form any iodide

Thallium(I) iodide and thallium(III) iodide differ in a subtle…

Answer: Tl³⁺ is a strong enough oxidant to oxidise I^-, so the stable species is Tl⁺ with I₃^-.

A Iodine cannot exist as I₃^-
B Tl³⁺ is a strong enough oxidant to oxidise I^-, so the stable species is Tl⁺ with I₃^-
C Tl³⁺ is much more stable than Tl⁺ and cannot oxidise iodide ions in dilute solution
D Thallium does not form any iodide

Correct answer: B. Tl³⁺ is a strong enough oxidant to oxidise I^-, so the stable species is Tl⁺ with I₃^-

Explanation: Because of the inert pair effect Tl³⁺ is a strong oxidiser; it would oxidise I^- to iodine, so the compound exists as Tl⁺(I₃)^-, i.e., thallium(I) triiodide.

Diamond's rigid 3D tetrahedral network makes it the hardest natural material, while graphite's flat hexagonal sheets are held together only by weak forces, letting them slide past each other (used as a lubricant and in pencils).

Concept context

Covers the Boron family (Group 13: B, Al) and the Carbon family (Group 14: C, Si, Ge, Sn, Pb). Key topics include Lewis acid behaviour of BF₃, borax bead test, silicates, silicones, allotropes of carbon, and trends in properties down the group.

Read the full p-Block Elements (Groups 13 & 14) notes →

Thallium(I) iodide and thallium(III) iodide differ in a subtle way: TlI3 is actually thallium(I) triiodide rather than thallium(III) iodide. This is best explained by the fact that:

Concept context

More p-Block Elements (Groups 13 & 14) questions

Thallium(I) iodide and thallium(III) iodide differ in a subtle way: TlI₃ is actually thallium(I) triiodide rather than thallium(III) iodide. This is best explained by the fact that: