What are the differences and similarities between elements, compounds and mixtures?

Atoms,
elements, compounds, and mixtures are all forms of matter. Matter is defined as anything that
has mass and volume.

Atoms, elements, and compounds are all pure substances.
A pure substance is made of only one type of particle. This contrasts mixtures, which are made
of more than one pure substances that do not chemically combine.

An atom is
the smallest unit of matter. An element is simply a type of atom that has a specific number of
protons. The periodic table is a chart that displays all of the different known
elements.

Compounds are composed of more than one atom. The atoms of
compounds are chemically bound via either ionic, covalent, or metallic bonds. Compounds consist
of two or more atoms of different elements.