SDSU Chemistry Placement Practice Test - Prep, Questions & Study Guide

Chlorine, which is located in Group 17 of the periodic table (also known as the halogens), has a total of 7 valence electrons. The valence electrons are those found in the outermost shell of an atom that can participate in chemical bonding. For chlorine, the electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁵. The outermost shell, or valence shell, is the third shell, which contains the 3s and 3p electrons.

In the case of chlorine, the 3s subshell holds 2 electrons, and the 3p subshell holds 5 electrons, resulting in a total of 7 valence electrons. This is a crucial factor in understanding chlorine's behavior in chemical reactions, as it typically seeks to gain one more electron to achieve a full outer shell, resembling the electron configuration of the nearest noble gas, argon. This tendency to reach 8 electrons in the valence shell is often related to the concept of stability and reactivity in chemistry.