OCR AS CHEMISTRY Definitions

Relative Atomic Mass

The relative atomic mass is the (weighted) mean mass of an atom of an element, compared to 1/12th the mass of an atom of Carbon-12.

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The relative isotopic mass is the mass of an isotope of an element relative to 1/12th the mass of an atom of Carbon-12.

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First ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms, to form 1 mole of gaseous 1+ ions.

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Electronegativity is a measure of how strongly an atom can attract the bonded pair of electrons.

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Isotopes are atoms of the same element/same number of protons, with a different number of neutrons/different mass number.

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Molar Mass is the mass per mole of a substance.

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The Empirical Formula is the simplest whole number ratio of atoms in each element present in a compound.

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The Molecular Fomula is the actual number of atoms of each element in a molecule.

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