CCEA Chemistry Unit 1 Definitions

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Atom

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A central positively charged nucleus containing protons and neutrons (most of the mass) surrounded by orbiting electrons in shells.

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Atomic number

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The number of protons in an atom.

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Atomic mass

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The total number of protons and neutrons in an atom.

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Isotope

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Atoms of an element with the same atomic number but a different mass number, indicating a different number of neutrons.

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Compound

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Two or more elements chemically combined.

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Ion

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A charged particle formed when an atom gains or loses electrons.

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Molecular ion

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A charged particle containing more than one atom.

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Cation

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A positively charged ion.

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Anion

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A negatively charged ion.

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Ionic bonding

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Involves attraction between oppositely charged ions; is typical of metal compounds.