Flashcards
Chem AS F321 definitions
Cards in this deck (22)
- 1Relative isotopic massThe mass of an atom of an isotope compared with one-twelfth of the mass of an atom of carbon-12.
- 2Relative atomic mass (Ar)The weighted mean mass of an atom of an element, compared with one-twelfth of the mass of an atom of carbon-12.
- 3IsotopesAtoms of an element with different numbers of neutrons and different masses.
- 4Relative molecular (Mr)/formula massThe weighted mean mass of a molecule/formula unit, compared with one-twelfth of the mass of an atom of carbon-12.
- 5Molar mass (M)The mass per mole of a substance (units g mol-1). Same as Mr in calculations - just that can be used for ions and elements too.
- 6Avogadro constant (NA)The number of entities per mole (6.02 x 10^23 mol-1 - number given on data sheet) i.e number of atoms per mole of the carbon-12 isotope.
- 7Amount of substanceThe quantity whose unit is the mole. Chemists use 'amount of substance' as a means of counting atoms.
- 8Mole (symbol 'mol')The unit for amount of substance (a mole is the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of C-12).
- 9Empirical formulaThe simplest whole number ratio of atoms of each element present in a compound.
- 10Molecular formulaThe ACTUAL number of atoms of each element in a molecule.
- 11"Anhydrous"Refers to a substance that contains no water molecules.
- 12"Hydrated"Refers to a crystalline compound containing water molecules.
- 13"Water of crystallisation"Refers to water molecules that form an essential part of the crystalline structure of a compound.
- 14OxidationLoss of electrons/increase in oxidation number.
- 15Reduction REMEMBER "OIL RIG"Gain of electrons/decrease in oxidation number.
- 16First ionisation energyThe energy required to remove one electron from each atom in one mole of GASEOUS ATOMS, to form one mole of GASEOUS 1+ IONS.
- 17Successive ionisation energyThe energy required to remove each electron in turn e.g. second ionisation energy - the energy required to remove one electron from each ION in one mole of gaseous 1+ IONS, to form one mole of gaseous 2+ IONS.
- 18Covalent bondA shared pair of electrons
- 19ElectronegativityThe ability of an atom to attract the bonding electrons in a covalent bond.
- 20Hydrogen bondA strong dipole-dipole attraction between an electron-deficient H atom on one molecule, and a lone pair of electrons on a highly electronegative atom on a DIFFERENT MOLECULE. (between molecules containing -OH (e.g. water) and -NH (e.g. NH3) groups.
- 21Metallic bondingThe attraction of positive ions to delocalised electrons.
- 22Ionic bondingElectrostatic attraction between oppositely-charged ions.
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- A Levels Chemistry AS revision Flashcards on Chem AS F321 definitions, created by lucy.wright73 on 30/01/2014.
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