(-0.1) 11) 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(e) + e E) S2-(g) -> S-(g) + e 12) Give the set of four quantum numbers that could represent the last electron added (using the Aufbau principle) to the Cl atom. A) n=3, l=1, m=1, ms=2 B) n=2, l=0, m=0, ms=1 C) n=3, l=2, m=1, ms=2 D) n=2, l=1, m=1, ms=2 E) n=3, l=1, m=1, ms=2
The Correct Answer and Explanation is:
Question 11: Which reaction below represents the second electron affinity of sulfur (S)?
The second electron affinity of sulfur refers to the addition of a second electron to the sulfur anion (S⁻), turning it into S²⁻. This is the key process for determining the second electron affinity. In this case, the correct answer is:
B) S⁻(g) + e⁻ → S²⁻(g)
Explanation:
Electron affinity is defined as the energy change that occurs when an electron is added to a neutral atom in the gas phase. The second electron affinity specifically refers to the addition of an electron to a negatively charged ion, which is typically an endothermic process because it involves adding an electron to a negatively charged species, which experiences repulsion from the existing electron(s). In the case of sulfur, after the first electron is added to form S⁻, a second electron can be added to form S²⁻. This process is represented by the equation in option B.
- Option A (S(g) + e⁻ → S⁻(g)) represents the first electron affinity, not the second.
- Option C (S(g) → S⁻(g) + e⁻) describes ionization, where an electron is removed from neutral sulfur.
- Option D (S(g) → S⁻(g) + e⁻) represents the removal of an electron from a neutral sulfur atom to form an anion, so it’s not relevant to electron affinity.
- Option E (S²⁻(g) → S⁻(g) + e⁻) is a dissociation reaction, where an electron is lost from S²⁻, but this is not related to the second electron affinity.
Question 12: Set of quantum numbers for the last electron added to a Cl atom
To find the correct set of quantum numbers for the last electron added to a chlorine (Cl) atom, we first need to consider the electron configuration of chlorine. Chlorine has an atomic number of 17, meaning it has 17 electrons. The electron configuration of chlorine is:
1s² 2s² 2p⁶ 3s² 3p⁵.
The last electron will be added to the 3p orbital, which is the 17th electron. The relevant quantum numbers are:
- n (principal quantum number): This corresponds to the energy level of the electron. For the last electron in chlorine, it is in the third energy level, so n = 3.
- l (azimuthal quantum number): This determines the shape of the orbital. For a p orbital, l = 1.
- m (magnetic quantum number): This determines the orientation of the orbital in space. The p orbitals have three possible orientations, represented by m = -1, 0, or +1. Since the last electron will be placed in the available 3p orbital, we choose m = 1.
- ms (spin quantum number): This represents the spin of the electron. Since it is the last electron, it will have a spin of ms = -1/2 (as per Hund’s rule, electrons fill orbitals singly before pairing).
Thus, the correct quantum numbers are:
D) n = 3, l = 1, m = 1, ms = -1/2
This corresponds to the last electron being added to the 3p orbital of chlorine.
