Atom - 1. The smallest particles of matter, that we cannot break down further by chemical means. 2. Consists of a nucleus and electrons that orbit around it whose mass is measured in atomic mass units. protons have a 1+ chemical charge while electrons have a 1- negative charge. 3. Every atom has an equal number of protons and electrons.

Element - Substances that cant be split into anything simpler by chemical means. An element contains only one kind of atom

Molecule - Consists of two or more atoms chemically bonded.

Proton/Atomic Number - The number of protons in an atom. You can identify an atom by the amount of protons because every atom has a different number.

Nucleon/Mass Number - The total number of protons and neutrons in an atom is called its nucleon number. Protons and neutons form the nucleus so called nucleons. Mass Number = number of protons + number of neutrons

Isotopes - Atoms of the same element with different numbers of neutrons. Isotopes of the same element have the same chemical properties because they have the same number of electrons and therefore the same electronic configuration.

Relative Atomic Mass - Average mass of an atom, taking account each isotope present in a naturally occurring sample of an element. calculate w mass number and relative abundances of all isotopes
(% of isotope A x mass of isotope A) + (% of isotope B x mass of isotope B)/100