DEFINITIONS Flashcards
Relative isotopic mass
the mass of an isotope compared with one-twelfth of the mass of an atom of carbon-12
Relative atomic mass, Ar
the weighted mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12
Relative molecular mass, Mr
the weighted mean mass of a molecule compared with one-twelfth of the mass of an atom of carbon-12
Relative formula mass, Mr
the weighted mean mass of a formula unit compared with one-twelfth of the mass of an atom of carbon-12
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
degenerate (when applied to orbitals)
of identical energy
amount of substance
the quantity whose unit is the mole. Used as a means of counting atoms.
the mole
the amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope
Avogadro constant
the number of atoms per mole of the carbon-12 isotope (6.02x1023 mol-1)
molar mass
the mass per mole of a substance in gmol-1
empirical formula
the simplest whole number ratio of atoms of each element present in a compound
molecular formula
the actual number of atoms of eachh element in a molecule
anhydrous
substance containing no water molecules
hydrated
crystalline compound containing water molecules
water of crystallisation
water molecules that form an essential part of the crystalline structure of a compound
Oxidation number
A measure of the number of electrons that an atom uses to bond with atoms of another element. Derived from a set of rules
Reducing agent
A reagent that reduces another species
Oxidising agent
A reagent that oxidises another species
Ionic bond
The electrostatic attraction between the oppositely charged ions
Giant ionic lattice
Three dimensional structure of opposite,y charged ions held together by strong ionic bonds
Covalent bonds
Bond formed by a shared pair of electrons
Lone pair
An outer shell pair of electrons that is not involved in chemical bonding
Dative covalent/coordinate bond
Shared pair of electrons provided by one of the bonding atoms only
Electronegativity
Measure of the attraction of a bonded atom for the pair of electrons in a covalent bond
Permanent dipole
A small charge difference across a bond that results from a difference in the electronegativities of the bonded atoms
polar molecule
has an overall dipole when you take into account any dipoles across the bonds
intermolecular force
an attractive force between neighbouring molecules
permanent dipole-dipole force
a weak attractive force between permanent dipoles in neighbouring polar molecules
van der Waals’ forces
attractive forces between induced dipoles in neighbouring molecules
a hydrogen bond
a strong dipole-dipole attraction between:
- an electron-deficit hydrogen atom on one molecule; and
- a lone pair of electrons on a highly electronegative atom on a different molecule
metallic bonding
the electrostatic attraction between positive metal ions and delocalised electrons
giant metallic lattice
3d structure of positive ions and delocalised electrons, bonded together by strong metallic bonds
simple molecular lattic
3-d structure of molecules, bonded together by weak intermolecular forces
giant covalent lattice
3-d structure of atoms, bonded together by strong covalent bonds
