Definitions:
1) Atom:the smallest particle of an element that can enter into a chemical reaction
2) Atomic Theory: an explanation of the structure of matter in terms of different combinations of very small particles (atoms)
3) Electron: a fundamental particle of matter having a negative charge
4) Nucleus: the dense positively charged central core of an atom
5) Proton: the positively charged particle in the nucleus of an atom
6) Neutron: an uncharged particle in the nucleus of an atom (*only contributes to mass)
7) Atomic Number: the number of protons in the nucleus of an atom (the ss# of the element)
8) Mass Number: the total number of protons and neutrons in the nucleus of an atom
9) Atomic Mass Unit: 1/12 the mass of a carbon-12 atom
10) Isotopes: atoms of the same element that have the same number of protons, but different number of neutrons thus having different masses
11) Ion: atoms of the same element that have the same number of protons, but different number of electrons (causing either a + or – net charge)
12) Nucleon: a term used to refer to the subatomic particles that reside in the nucleus (protons and neutrons)
13) Mass Spectrometer: an instrument used to determine the mass to charge ratio of an atom
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