Electron affinity Transitional Reasoning Download PDF

Questions

1. 1.

   A student investigating the first electron affinities of Group 17 elements notices an anomaly: although electron affinity generally becomes less exothermic down a group as atomic radius increases, chlorine has a more exothermic value (-349 kJ/mol) than fluorine (-328 kJ/mol). To explain this deviation from the standard periodic trend, the student analyzes their atomic structures. Which of the following statements provides the scientifically valid explanation for why chlorine releases more energy than fluorine upon gaining an electron?

   • A) Fluorine's incoming electron enters an exceptionally small and dense 2p subshell, causing strong interelectronic repulsions that diminish the net energy released compared to the larger 3p subshell of chlorine.
   • B) Chlorine has a higher effective nuclear charge than fluorine, which exerts a stronger attraction on the incoming valence electron despite the greater shielding.
   • C) Fluorine requires energy to promote an electron into the 3s orbital prior to electron capture, making the overall process significantly less exothermic.
   • D) Chlorine exhibits an extra core electron shell that completely eliminates electron-electron repulsion among its valence electrons.