Chemistry AS ocr Key definitions for the unit 1 ocr chemistry as topic 4.0 / 5 based on 7 ratings ? ChemistryBonding & shapesASOCR Created by: bexCreated on: 03-01-13 14:11 Isotopes atoms of the same element with different numbers of neutons 1 of 25 Relative atomic mass the mean mass of an atom compared with 1/12th of a carbon-12 atom 2 of 25 Ion have different numbers of protons and electrons 3 of 25 Mole the amount of any substance containing as many particles as there are carbon in exactly 12g of carbon-12 isotope 4 of 25 Molar mass mass of one mole 5 of 25 Avogadro constant 6.02x10^23 6 of 25 Empirical Formula the simplest whole-number ratio of a saturated molecule to make an unsaturated molecule 7 of 25 Salt a chemical compound formed from an acid, when a h+ ion from the acid has been replaced by a metal ion or another positive ion 8 of 25 Oxidation is loss of electrons (increase in oxidation number) 9 of 25 Reduction is gain of electrons (decrease in oxidation number) 10 of 25 Sub-shell a group of the same type of atomic orbitals within a shell 11 of 25 Orbital the space in which the electron moves 12 of 25 First ionisation energy the energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ atoms 13 of 25 Ionic bonding the electrostatic attraction between oppositely charged ions 14 of 25 Covalent bonding shared pair of electrons 15 of 25 Metallic bonding the electrostatic attraction between positive metal ions and delocalised electrons 16 of 25 Linear Molecules 2 electron pairs on central atoms 17 of 25 Trigonal planar 3 electron pairs on central atom (no lone pairs) 18 of 25 Tetrahedral 4 electron pairs on central atom (no lone pairs) 19 of 25 Trigonal pyramidal 4 electron pairs on central atom (one lone pair) 20 of 25 Non-linear 4 electron pairs on central atom (2 lone pairs) 21 of 25 Octahedral 6 electron pairs on central atom (no lone pairs) 22 of 25 Electronegativity a measure of attraction of a bonded atom for the pair of electrons in a covalent bond 23 of 25 van der Waals' forces very weak attractive forces between induced dipoles in neighbouring molecules 24 of 25 Disproportionation the oxidation and reduction of the same element in a redox reaction 25 of 25
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