Which reaction below represents the second electron affinity of S? A) S(g) + e? ? S?(g) B) S?(g) + e? ? S²?(g) C) S(g) ? S?(g) + e? D) S?(g) ? S(g) + e? E) S²?(g) ? S?(g) + e
The Correct Answer and Explanation is:
The correct answer is B) S⁻(g) + e⁻ → S²⁻(g).
Explanation:
The second electron affinity refers to the process in which an atom or ion gains a second electron, forming a negatively charged ion. The electron affinity generally involves the addition of an electron to a neutral atom, resulting in the formation of a negative ion. The second electron affinity specifically refers to the addition of an electron to a negatively charged ion, and it is always endothermic (requires energy) because the addition of a negatively charged electron to an already negatively charged ion results in repulsion between the two negative charges.
Let’s break down the options:
- Option A: S(g) + e⁻ → S⁻(g)
This represents the first electron affinity of sulfur. The process here involves adding an electron to a neutral sulfur atom, producing a negatively charged ion, S⁻. This is the first electron affinity, not the second. - Option B: S⁻(g) + e⁻ → S²⁻(g)
This is the correct representation of the second electron affinity of sulfur. Here, we are adding a second electron to the negatively charged sulfur ion (S⁻), resulting in the formation of S²⁻. This process is endothermic, as the addition of another negative electron to an already negatively charged ion requires energy to overcome the repulsive forces. - Option C: S(g) → S⁻(g) + e⁻
This also represents the first electron affinity of sulfur. It shows sulfur gaining an electron to form a negative ion, which is the initial electron affinity process. - Option D: S⁻(g) → S(g) + e⁻
This is the opposite of the electron affinity process, as it depicts the ion S⁻ losing an electron to become a neutral sulfur atom. This would represent an ionization process, not electron affinity. - Option E: S²⁻(g) → S⁻(g) + e⁻
This represents the removal of an electron from the S²⁻ ion, which is the process of ionization (the reverse of gaining an electron), not electron affinity.
Thus, the second electron affinity specifically involves the addition of an electron to an already negatively charged ion, making Option B the correct choice.
