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Cards In This Set
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Matter
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Anything that occupies space and has mass
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Element
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A substance that cannot be broken down to other substances by chemical means. Scientists recognize 92 chemical elements occurring in nature
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Trace Elements
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An element that is essential for the survival of an organism but only in minute quantities
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Compound
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A substance containing two or more elements in a fixed ratio. For example, table salt (NaCl) consists of one atom of the element sodium (Na) for every atom of chlorine (Cl)
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Atom
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The smallest unit of matter that retains the properties of an element
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Proton
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A subatomic particle with a single positive electrical charge, found in the nucleus of an atom
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Electron
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A subatomic particle with a single negative electrical charge. One or more electrons move around the nucleus of an atom
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Nucleus
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(1) An atom’s central core, containing protons and neutrons. (2) The genetic control center of a eukaryotic cell
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Atomic Number
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The number of protons in the nucleus of one atom
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Mass Number
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The sum of the number of protons and neutrons in an atom’s nucleus
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Atomic Mass
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The approximate total mass of an atom; also called atomic weight. Given as a whole number, the atomic mass approximately equals the mass number
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Isotopes
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A variant form of an atom. Isotopes of an element have the same number of protons but different numbers of neutrons
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Radioactive Isotope
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An isotope whose nucleus decays spontaneously, giving off particles and energy
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Electron Shells
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An energy level representing the distance of an electron from the nucleus of an atom
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Ion
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An atom or molecule that has gained or lost one or more electrons, thus acquiring an electrical charge
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