All compounds that end in "oxide" have oxygen as one of their constituent elements.

Here's why:

* Oxide is a chemical term that refers to a compound containing oxygen.

* The suffix "-ide" in chemistry generally indicates a binary compound, meaning it contains two elements.

* Therefore, any compound ending in "oxide" will contain oxygen and one other element.

Examples:

* Iron oxide: Contains iron (Fe) and oxygen (O).

* Carbon dioxide: Contains carbon (C) and oxygen (O).

* Sodium oxide: Contains sodium (Na) and oxygen (O).