Q.Which element from the following pairs has higher ionization enthalpy? B and Tl, N and Bi

Group 13, the boron family (B, Al, Ga, In, Tl), shares the general outer electronic configuration ns2np1. Boron is a metalloid, hard and glossy but a poor electrical conductor; the rest of the group are reactive metals, with aluminium the third most abundant element in the earth's crust. Atomic radius and ionic radius generally increase down the group as new shells are added, but gallium is anomalously smaller than aluminium because ten of the eighteen extra electrons added between Al and Ga fill the poorly-shielding inner 3d subshell, letting the increased nuclear charge pull Ga's outer electrons in more tightly. First ionization enthalpy generally falls down the group but shows similar irregular upward blips at ga …