Consider the following elements In, Tl, Al, Pb, Sn and Ge . The most stable oxidation states of elements with highest and lowest first ionisation enthalpies, respectively, are

Find the most stable oxidation states of the elements with highest and lowest first ionisation enthalpies among In, Tl, Al, Pb, Sn, Ge.

The elements belong to Groups 13 (Al, In, Tl) and 14 (Ge, Sn, Pb). General trend: IE decreases down a group but with irregularities due to poor shielding by d and f electrons. Among these, Ge has the highest IE (smaller size, Group 14, Period 4) and In or Tl has the lowest (larger size, Group 13). Specifically, Tl has a relatively high IE due to the inert pair effect and poor shielding. In actually has the lowest first IE among these elements.

Ge (highest IE) has electronic config [Ar]3d¹⁰4s²4p². Its most stable oxidation state is +4 (using all 4 valence electrons). The inert pair effect is weak for lighter elements.

In (lowest IE) has config [Kr]4d¹⁰5s²5p¹. Its most stable oxidation state is +3 (using all 3 valence electrons). Unlike Tl, In does not show a strong inert pair effect.

The most stable oxidation states are +4 (highest IE element) and +3 (lowest IE element). The correct answer is Option C: +4 and +3.