AS LEVEL CHEMISTRY UNIT ONE KEY DEFINITIONS LIST

I have taken all the definitions from the first unit from my ocr text book but I think they should apply to most other chemistry as level courses. Hope it helps :)

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  • Created on: 13-01-13 18:58
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Unit F321: Atoms, Bonds and Groups
Definitions
Atoms and Electron Structure
Isotopes atoms of an element with different numbers of neutrons and
different masses
Relative atomic mass the weighted mean mass of an atom of an element
compared to 1/12 of the mass of an atom of carbon12
Relative isotopic mass mass of an atom of an isotope relative to 1/12 of the mass
of an atom of carbon12
Relative molecular mass the weighted mean mass of a molecule compared with 1/12
of the mass of an atom of carbon12
Relative formula mass the weighted mean mass of a formula unit compared with
1/12 of the mass of an atom of carbon12
Avogadro constant the number of atoms per mole of the carbon12 isotope
(6.02x1023mol1
Mole the amount of any substance containing as many particles as
there are carbon atoms in exactly 12g of the carbon12
isotope
Molar mass the mass per mole of a substance. The units of molar mass
are gmol1
Empirical formula the simplest wholenumber ratio of atoms of each element
present in a compound
Molecular formula the actual number of atoms of each element in a molecule
Orbital a region within an atom that can hold up to 2 electrons with
opposite spins
Species any type of particle that takes part in a chemical reaction
1st 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+ ions.
Successive ionisation energy a measure of the energy required to remove each electron in
turn.
Electron shielding the repulsion between electrons in different inner shells.
Shielding reduces the net attractive force from the positive
nucleus on the outershell electrons

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Acids and bases
Acid proton donor (H+ donor)
Base proton acceptor (H+ acceptor)
Salt any chemical compound formed from an acid when a H+ion
from the acid has been replaced by a metal ion on another
positive ion
Water of crystallisation
Hydrated refers to a crystalline compound containing water molecules
Anhydrous refers to a substance that contains no water molecules
Water of crystallisation refers to water molecules that form an essention part of the
crystalline structre of a compound
Bonding
Ionic bond the electrostatic attraction…read more

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Van der Waal forces attractive forces between induced dipoles in neighbouring
molecules
Metallic bonding the electrostatic attraction between positive metal ions and
delocalised electrons
Giant metallic lattice a threedimensional structure of positive ions and
delocalised electrons, bonded together by strong metallic
bonds
Hydrogen bond a strong dipoledipole attraction between an electron
deficient hydrogen atom on one molecule and a lone pair of
electrons on a highly electronegative atom on a different
molecule
Redox
Oxidation loss of electrons or increase in oxidation number
Reduction gain of…read more

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