which two molecules are compounds?
Molecules containing more than two atoms are termed polyatomic molecules, e.g., carbon dioxide (CO2) and water (H2O). Polymer molecules may contain many thousands of component atoms. A water molecule is made up of two hydrogen atoms and one oxygen atom. A single oxygen atom contains six electrons in its outer shell, which can hold a total of eight electrons. When two hydrogen atoms are bound to an oxygen atom, the outer electron shell of oxygen is filled. EncyclopÃ¦dia Britannica, Inc.