JEE Main · 2026 · 04 Apr 2026 · Shift 2 · p-Block Elements

Germanium has a Pauling electronegativity of $1.8$, and the group-13 element matching this to one decimal is thallium, so $E$ is $\mathrm{Tl}$. Thallium shows a pronounced inert-pair effect: the $6s^2$ pair resists removal, so $\mathrm{T}{\mathrm{l}}^{+}$ is far more stable than $\mathrm{T}{\mathrm{l}}^{3+}$, meaning ${\mathrm{E}}^{3+}$ is less stable than ${\mathrm{E}}^{+}$ and cannot act as a reducing agent. Instead $\mathrm{T}{\mathrm{l}}^{3+}$ readily gains electrons to fall back to $\mathrm{T}{\mathrm{l}}^{+}$, so it is a good oxidising agent, and the reduction potential $E^{\circ }(\mathrm{T}{\mathrm{l}}^{3+}/Tl)$ is positive (about $+0.72\mathrm{V}$). The correct statements about ${\mathrm{E}}^{3+}$ are that it can act as an oxidising agent and that its ${\mathrm{E}}^{3+}/E$ standard electrode potential is positive.