JEE Main · 2026 · 23 Jan 2026 · Shift 1 · Classification of Elements and Periodicity

The ionic radii of the ${\text{M}}^{3+}$ ions of group 13 increase down the group (${\text{B}}^{3+}<{\text{Al}}^{3+}<{\text{Ga}}^{3+}<{\text{In}}^{3+}<{\text{Tl}}^{3+}$), so statement A is wrong. Electronegativity does not fall steadily down the group; after aluminium it rises again because of d- and f-block contraction, so statement B is wrong. Boron, the smallest element, has the highest first ionisation enthalpy in the group, so statement C is true. The trichlorides and triiodides of group 13 are largely covalent, so statement D is true. The correct statements are C and D.