What is the oxidation state of chlorine in most compounds?

The oxidation state of chlorine in most of its compounds is indeed -1. This is primarily due to the fact that chlorine is a halogen, and halogens typically acquire an oxidation state of -1 when they form compounds with metals or with nonmetals that are less electronegative than themselves.

In these compounds, chlorine gains an electron, filling its outer shell and achieving a more stable electronic configuration. For example, in sodium chloride (NaCl), chlorine has an oxidation state of -1 because it accepts an electron from sodium, which donates an electron and has a positive oxidation state of +1.

While chlorine can exhibit other oxidation states in specific compounds (such as +1, +3, +5, and +7), these occur in less common scenarios, particularly when chlorine is combined with highly electronegative elements or in oxoanions. However, the most prevalent and stable oxidation state of chlorine in the majority of its compounds is indeed -1.