A pure substance made of only one kind of atom.

A substance made up of atoms of two or more different elements joined by chemical bonds.

A table that classifies elements by their physical and chemical properties; rows are called periods; columns are called groups.

A measure of the amount of matter in an object.

The amount of space matter takes up.

Matter is not created nor destroyed in any chemical or physical change.

A subatomic particle that has a positive charge and that is found in the nucleus of an atom.

A subatomic particle that has no charge and that is found in the nucleus of an atom.

A subatomic particle that has a negative charge.

Number of protons in the nucleus.

Number of protons + neutrons.

Average mass of all naturally-occurring isotopes of a given element, measured in AMU.

Atoms of the same element that have different numbers of neutrons.

Particles that make up an atom; protons, neutrons, and electrons

Horizontal rows on the periodic table

Vertical columns on the periodic table