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energy level

the possible energies that electrons in an atom can have

valence electron

an electron that is in the highest occupied energy level of an atom


an atom or group of atoms that has a positive or negative charge


a neutral group of atoms that are joined together by one or more covalent bonds


a substance that is made from 2 or more simple machines that operate together

ionic bond

the force that hold cations and anions together


a chemical bond in which 2 atoms share a pair of valence electrons

octet rule

atoms have a fuller shell are stable. These atoms don't tend to gain or lose electrons to become stable.

periodic law

the pattern of repeating properties displayed by elements in the periodic table


elements with properties that fall between those of metals and non-metals

noble gas

the element group 8A of the periodic table


the dense, positively charged mass located in the center of an atom


a positively charged subatomic particle that is found in the nucleus of an atom. mass = 1 amu

Atomic Mass Unit

one twelfth the mass of a carbon-12 atom


a neutral subatomic particle that is found in the nucleus of an atom. mass = 1amu

atomic number

a unique number for each element that equals the number of protons in an atom of that element


atoms of a given element that have different numbers of neutrons and different mass numbers

mass number

the sum of the number of protons and neutrons in the nucleus of an atom


a negatively charged subatomic particle that is found in the space outside the nucleus of an atom. mass = 0 amu

electron cloud

a visual model of the most likely locations for the electrons in an atom

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