66 terms

OCR Chemistry F321 Keywords

Some key terms from the OCR F321 spec.
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acid
A species that is a proton donor.
alkali
A type of base that dissolves in water to form hydroxide ions, OH- (aq).
amount of substance
The quantity whose unit is the mole.
anhydrous
A substance containing no water molecules.
anion
A negatively charged ion.
orbital
A region within an atom that can hold up to two electrons with opposite spins.
atomic number
The number of protons contained in the nucleus of an atom.
avogadro constant
The number of atoms per mole of the carbon-12 isotope.
base
A species that is a proton acceptor.
cation
A positively charged ion.
compound
A substance formed from two or more chemically bonded elements in a fixed ratio.
concentration
The amount of solute, in mol, per 1dm3 of solution.
dative bond
A shared pair of electrons provided by only one of the bonding atoms.
covalent bond
A bond formed by a shared pair of electrons.
delocalised electrons
Electrons shared between more than two atoms.
displacement
A more reactive element displaces a less reactive element from a solution of the latter's ions.
disproportionation
The oxidation and reduction of the same element in a redox reaction.
configuration
The arrangement of electrons in an atom.
electronegativity
A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.
electron shielding
The repulsion between electrons in different inner shells.
empirical formula
The simplest whole-number ratio of atoms of each element present in a compound.
giant covalent lattice
A three-dimensional structure of atoms held together by strong covalent bonds.
giant ionic lattice
a three-dimensional structure of oppositely charged ions held together by strong ionic bonds.
giant metallic lattice
A three-dimensional structure of metal cations and a sea of delocalised electrons held together by strong metallic bonds.
hydrated
crystalline compounds that contain water molecules.
hydrogen bond
A strong dipole-dipole 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.
intermolecular force
An attractive force between neighbouring molecules.
ion
A positively or negatively charged atom or group of atoms.
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+ ions,
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.
successive ionisation energy
A measure of the energy required to remove one electron in turn.
isotope
An atom of the same element but with a different number of neutrons.
limiting reagent
The substance in a chemical reaction that runs out first.
lone pair
An outer shell pair of electrons that is not involved in bonding.
mass number
The number of particles in the nucleus.
metallic bond
The electrostatic attraction between positive metal ions and a sea of delocalised electrons.
molar mass
The mass per mole of a substance.
molar volume
The volume per mole of a gas.
mole
The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope.
molecule
A small group of atoms held together by covalent bonds.
oxidation
Loss of electrons to produce an increase in oxidation number.
oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element.
period
A horizontal row of elements in the periodic table.
periodicity
A regular periodic variation of properties of elements with atomic number and position in the periodic table.
permanent dipole
A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms.
dipole-dipole force
An attractive force between permanent dipoles in neighbouring polar molecules.
polar bond
A bond with a permanent dipole.
polar molecule
A molecule with an overall dipole.
precipitation
The formation of a solid from a solution during a chemical reaction.
quantum number
A number representing the overall energy of each orbital, which increases with distance from the nucleus.
redox
A reaction in which both reduction and oxidation takes place.
reducing agent
A reagent that reduces another species.
reduction
Gain of electrons and thus a decrease in oxidation number.
atomic mass
The weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of carbon-12.
formula mass
The weighted mean mass of a formula unit compared with 1/12th of the mass of an atom of carbon-12.
isotopic mass
The mass of an atom of an isotope compared with 1/12th of the mass of an atom of carbon-12.
molecular mass
The weighted mean mass of a molecule compared with 1/12th of the mass of an atom of carbon-12.
salt
A chemical compound formed from an acid when a H+ ion has been replaced by a metal or ammonium ion.
shell
A group of atomic orbitals with the same principal quantum number.
molecular lattice
A three-dimensional structure of molecules bonded together by weak intermolecular forces.
species
Any type of particle that takes part in a chemical reaction.
standard solution
A solution of known concentration, normally used in titrations.
stoichiometry
The molar relationship between the relative quantities of substances taking part in a reaction.
sub shell
A group of the same type of atomic orbitals within a shell.
decomposition
The breaking up of a chemical substance with heat into at least two chemical substances.
van der waals
Very weak attractive forces between induced dipoles in neighbouring molecules.
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