The electron configuration describes the arrangement of electrons within an atom's orbital shells. Chlorine (Cl) has an atomic number of 17, meaning a neutral chlorine atom has 17 electrons. The filling of electron orbitals follows the Aufbau principle (lowest energy levels first), resulting in the following configuration:

• 1s²: The first energy level, s-subshell, holds 2 electrons.
• 2s²: The second energy level, s-subshell, holds 2 electrons.
• 2p⁶: The second energy level, p-subshell, holds 6 electrons.
• 3s²: The third energy level, s-subshell, holds 2 electrons.
• 3p⁵: The third energy level, p-subshell, holds the remaining 5 electrons (2 + 2 + 6 + 2 + 5 = 17 electrons in total).