Why is the electron affinity of each group 5A element more positi...

Question

Why is the electron affinity of each group 5A element more positive than that of each corresponding group 4A element? Use the outer electron configurations for these columns to suggest a reason for this observation.

Accepted Answer

Identify the outer electron configurations for Group 4A and Group 5A elements. Group 4A elements have the general outer electron configuration of $ ns^2 np^2 $, while Group 5A elements have $ ns^2 np^3 $.. Understand electron affinity: it is the energy change when an electron is added to a neutral atom in the gas phase, forming a negative ion. A more negative electron affinity indicates a greater tendency to gain an electron.. Consider the stability of half-filled orbitals. Group 5A elements have half-filled $ p $ orbitals ($ np^3 $), which are relatively stable due to electron pairing and exchange energy.. Adding an electron to a Group 5A element results in a $ np^4 $ configuration, which is less stable than the half-filled $ np^3 $ configuration, making the electron affinity less negative (more positive).. In contrast, Group 4A elements, with $ np^2 $ configuration, gain stability when an electron is added to form $ np^3 $, resulting in a more negative electron affinity compared to Group 5A.