Topic 3 : Def Flash Cards

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Atom

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The basic unit of a chemical element.

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Electron

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A stable subatomic particle with a charge of negative electricity, found in all atoms and acting as the primary carrier of electricity in solids.

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Nucleus

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The positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.

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Proton

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A stable subatomic particle occurring in all atomic nuclei, with a positive electric charge equal in magnitude to that of an electron.

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Neutron

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A subatomic particle of about the same mass as a proton but without an electric charge, present in all atomic nuclei except those of ordinary hydrogen.

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Atomic number

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The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

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Isotope

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Each of two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties.

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Mass number

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The total number of protons and neutrons in a nucleus.

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Atomic mass

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The mass of an atom of a chemical element expressed in atomic mass units.

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Periodic table

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A table of the chemical elements arranged in order of atomic number, usually in rows, so that elements with similar atomic structure (and hence similar chemical properties) appear in vertical columns.