Why do the oxygen ion, O2−, and the sulfide ion, S2−, have negative charges?
The Correct Answer and Explanation is:
The oxygen ion (O²⁻) and sulfide ion (S²⁻) both carry negative charges due to their electronic configurations and the nature of ionic bonding. Atoms can gain or lose electrons to achieve a more stable electronic configuration, typically resembling that of noble gases. For oxygen and sulfur, gaining electrons allows them to fill their outer electron shells, resulting in negatively charged ions.
Oxygen Ion (O²⁻)
Oxygen has an atomic number of 8, meaning it has 8 electrons in its neutral state, with the electronic configuration of 1s² 2s² 2p⁴. This configuration indicates that oxygen has six electrons in its outer shell (the second shell), which can hold up to eight electrons. To attain a stable octet configuration (eight electrons in the outer shell), oxygen needs to gain two additional electrons. When oxygen gains these two electrons, it becomes an oxide ion (O²⁻), with a total of ten electrons and a charge of -2. This negative charge reflects the surplus of electrons compared to the number of protons in the nucleus.
Sulfide Ion (S²⁻)
Sulfur has an atomic number of 16, meaning it possesses 16 electrons in its neutral state, with the electronic configuration of 1s² 2s² 2p⁶ 3s² 3p⁴. Similar to oxygen, sulfur has six electrons in its outermost shell and requires the addition of two electrons to achieve a full outer shell configuration of eight electrons, leading to stability. When sulfur gains two electrons, it forms a sulfide ion (S²⁻), resulting in a total of eighteen electrons and a charge of -2. The negative charge indicates that there are two more electrons than protons.
Conclusion
In summary, both O²⁻ and S²⁻ ions acquire negative charges by gaining electrons to achieve stable electronic configurations. This process is driven by the fundamental principle of atoms striving for stability, typically represented by the octet rule. Their formation illustrates how nonmetals can attain stability through the formation of negatively charged ions in ionic compounds.