Atom: An atom is the simplest and smallest part of an element. It cannot be broken by any chemical means.
Electron: An electron is a negatively (-1) charged component of an atom, Electrons exist outside of and surrounding the atom nucleus. Mass = 1/2000.
Proton: A component of an atomic nucleus with a mass defined as 1 and a charge of +1.
Neutron: A component of an atomic nucleus with a mass defined as 1 and a charge of 0.
Nucleus: The centre of an atom. It is composed of neutrons and protons, and possesses most of the mass.
Chemical change: A change that results in new substances being formed. Chemical changes are usually difficult to reverse.
Physical change: A change that results in a substance changing state. Generally, they are easily reversed.
Element: A substance composed of only one type of atom. The Periodic Table of Elements shows the elements in order of increasing atomic number.
Compound: A substance made of two or more different atoms chemically combined.
Mixture : A substance made of two or more different elements or compounds that are not chemically combined.