Chapter 3 - Active Learning Questions - Page 150: 8

See explanation

The second electron affinity values for oxygen and sulfur are unfavorable because they involve adding an electron to an already negatively charged ion. When oxygen or sulfur gains an electron to form a singly charged negative ion (O²⁻ or S²⁻), there is an increase in electron-electron repulsions due to the addition of another negative charge. The repulsions make the process endothermic and energetically unfavorable, resulting in a positive second electron affinity value.