Important Terms

1. Important Terms • ATOM - Smallest unit of an element that keeps its chemical properties • ELEMENT – Unique substance with the same number of protons in every atom, that cannot be broken down by chemical means • MOLECULE - Smallest unit of a compound that keeps its chemical properties (made of two or more atoms) • COMPOUND - Substance that can be broken into separate elements by chemical reactions • ELECTRON (e-) - Particle moving around the nucleus of an atom with a negative charge; it does NOT have a definitive position in the energy level; (mass = 1/2000 amu) • NEUTRON (N) - Particle in the nucleus of an atom with no charge; (mass = 1 amu) • PROTON (P) - Particle in the nucleus of an atom with a positive charge; (mass = 1 amu) • ION - Electrically charged atom (i.e., excess positive or negative charge) • NUCLEUS - Dense, central core of an atom, does not have a definitive membrane • ATOMIC MASS – total mass of the protons and neutrons in an atom • ISOTOPES - atoms of an element each form having a different atomic mass. Isotopes of an element have the same number of protons but different numbers of neutrons – which ultimately alters the mass