Question

Which one of the following trihalide oxidation state of metal is not +3?

• A. $BC{l}_3$
• B. $AlC{l}_3$
• C. $Tl{I}_3$
• D. $BB{r}_3$

Answer 1

The correct option is C $Tl{I}_3$

Group 13 elements react with halogen to form trihalides (except $Tl{I}_3$).
$2E\left(s\right)+3X_2\left(g\right)\to 2E{X}_3\left(s\right)$
(X = F, Cl Br, I)
In $Tl{I}_3$, oxidation state of Tl is +1.