A molecule that contains two atoms is called a diatomic molecule. Some examples of diatomic molecules are oxygen, nitric oxide and hydrogen. A molecule is defined as a substance that contains two or more atoms.
In basic chemistry, the simplest form of most matter is a compound. The definition of a compound is two or more elements that are chemically combined. Since a molecule contains two or more atoms, it is a compound. A diatomic molecule is one that contains two identical atoms from the same element. There are also molecules that contain three atoms. These are referred to as triatomic molecules. Some examples of triatomic molecules are sulfur dioxide, carbon dioxide and ozone. Inert gases are classified as molecules as well; however, they only contain one atom and are referred to as monatomic molecules.
A compound usually consists of atoms of different chemical elements bonding together. A good example is the water compound of H2O. This compound is made up of a hydrogen molecule, which is formed by combining two atoms of hydrogen with one oxygen atom.
There are three types of chemical bonds: ionic, covalent and hydrogen. An ionic bond transfers electrons from one atom to another. A covalent bond shares atoms and a hydrogen bond is just a weak, temporary bond.