How many electrons in total are found in a S2- anion?
The correct answer and explanation is:
The total number of electrons in a S2−\text{S}^{2-} anion is 18 electrons.
Explanation:
The sulfur atom has an atomic number of 16, meaning it normally has 16 protons and 16 electrons when it is neutral. The number of electrons in an atom equals its atomic number because the atom is electrically neutral, with the number of positive protons balanced by the number of negative electrons.
When sulfur forms a S2−\text{S}^{2-} anion, it gains two additional electrons. This happens because sulfur has six valence electrons in its outer shell and needs two more electrons to achieve a stable octet configuration (similar to the nearest noble gas, argon). By gaining these two electrons, the sulfur atom now has a total of: 16 (original electrons)+2 (additional electrons)=18 electrons.16 \text{ (original electrons)} + 2 \text{ (additional electrons)} = 18 \text{ electrons}.
The extra electrons make the sulfur atom negatively charged, as the number of electrons now exceeds the number of protons. The S2−\text{S}^{2-} anion thus has a 2- charge, reflecting the gain of two electrons.
The electron configuration for S2−\text{S}^{2-} can be written as: 1s2 2s2 2p6 3s2 3p61s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6
This shows that the S2−\text{S}^{2-} ion has a completely filled third energy level (3p^6), which gives it the same electron configuration as argon. The extra electrons and the resulting negative charge contribute to the stability of the ion.
Thus, the total number of electrons in a S2−\text{S}^{2-} anion is 18.