Atoms, Elements, Molecules, and Compounds

The smallest particle of an element that can exist.

A pure chemical substance that cannot be physically split into a more simple substance. Each is made of one type of atom. Carbon, mercury and hydrogen are examples.

The smallest particle of a substance that can exist. It is composed of two or more atoms.

A substance made of atoms from two or more elements.

A particle of matter that has a positive electrical charge and forms part of the nucleus of an atom.

A particle of matter that has no electrical charge and forms part of the nucleus of an atom.

A particle of matter that has a negative electrical charge and travels around the nucleus of an atom.

Number of protons. Top number in the element box.

Number of protons plus neutrons. Bottom number in the element box.

Tiny number to the right of the element symbol. Tells you how many atoms of that element.

A one or two letter representation of an element.