What is the full electron configuration for the anion Cl⁻?

Chlorine, in its neutral state, has an atomic number of 17, meaning it contains 17 electrons. The electron configuration of a neutral chlorine atom is written as 1s² 2s² 2p⁶ 3s² 3p⁵, which represents the distribution of these electrons among the various atomic orbitals.

When chlorine gains an electron to form the anion Cl⁻, it now contains 18 electrons. This additional electron fills the 3p subshell, resulting in a complete outer shell. The full electron configuration for the Cl⁻ anion thus becomes 1s² 2s² 2p⁶ 3s² 3p⁶.

The correct answer reflects this configuration as it shows all 18 electrons arranged appropriately. The outer shell is now fully occupied, indicating that Cl⁻ is iso-electronic with the noble gas argon, achieving a stable electronic arrangement.

Choices that suggest fewer electrons or incorrectly distribute the electrons in the p subshell do not accurately represent the anion’s full electron configuration. Thus, the choice capturing the complete configuration of the anion Cl⁻ aligns with the principles of electron configuration and the resulting stability in filled