1s² 2s² 2p⁶ 3s² 3p⁶
In other words, a chloride ion has two electrons in the first energy level, eight electrons in the second energy level, and eight electrons in the third energy level. The outermost energy level (the third energy level) is completely filled, which gives the chloride ion a stable electron configuration.
Chloride ions are formed when chlorine atoms gain one electron. Chlorine atoms have seven electrons in their outermost energy level, so they need to gain one more electron to achieve a stable electron configuration. When a chlorine atom gains an electron, it becomes a chloride ion.
Chloride ions are essential for many biological processes, such as the regulation of fluid balance and the transmission of nerve impulses. They are also found in many common household products, such as table salt (NaCl) and hydrochloric acid (HCl).
