Four different graphs are plotted for the variation of a periodic property (on the y-axis) against the first four halogens ( F , Cl , Br , I ) arranged in increasing order of atomic number (on the x-axis). Graph A shows a strictly decreasing curve. Graph B shows a strictly increasing curve. Graph C shows a curve that increases from F to Cl , then decreases for Br and I . Graph D shows a curve that decreases from F to

Step-by-step solution

The magnitude of electron gain enthalpy generally decreases down a group as the atomic size increases. However, due to the very small size of the F atom, there are strong interelectronic repulsions in its relatively compact 2 p subshell. As a result, the incoming electron experiences less attraction compared to the larger Cl atom. Therefore, the magnitude of electron gain enthalpy increases from F to Cl , and then follows the regular trend of decreasing from Cl to Br to I . The order of magnitude is: Cl > F > Br >