An element with an oxidation state of -2 means that the element has gained two electrons. Elements that commonly exhibit an oxidation state of -2 include:

Oxygen (O): Oxygen typically forms a -2 oxidation state when it bonds with metals or hydrogen. For example, in the oxide ion (O2-), oxygen has a -2 oxidation state.

Sulfur (S): Sulfur can exhibit a -2 oxidation state in various compounds, such as sulfide ions (S2-) and hydrogen sulfide gas (H2S).

Selenium (Se): Selenium shares similarities with sulfur and can also adopt a -2 oxidation state in compounds like selenide ions (Se2-) and hydrogen selenide gas (H2Se).

Tellurium (Te): Tellurium, like selenium, can display a -2 oxidation state in telluride ions (Te2-) and hydrogen telluride gas (H2Te).

Polonium (Po): Polonium, a radioactive element, exhibits a -2 oxidation state in polonide ions (Po2-) and hydrogen polonide gas (H2Po).

These elements tend to gain electrons to achieve a stable electron configuration and form negative ions or covalent bonds with other elements.