Empirical formula - the simplest whole number molar combining ratio of the of the numbers of atoms of the different elements present in the compound
Molecular formula - the formula that the compound actually has, this will either be the empirical formula itself or a whole number multiple of it
Displayed formula - when the compound is drawn out as it is
Structural formula - gives the order that the atoms are found in
Skeletal formula - the simplest representation of a formula (where carbons and hydrogens aren't written down)
Hydrocarbons - contain hydrogen and carbon ONLY. Saturated compounds only contain single C-C bonds, unsaturated compounds contain at least one C=C double bond.
Homologous Series - a family of organic compounds that all comply to the same general formula, they all have similar chemical and physical properties.
Functional Group - the functional group 'does the chemistry' which is connected to the hydrocarbon backbone
Isomer - compounds that share a common molecular formula, but have different structures
Homlytic Fission - this is when a bond breaks and the electrons are distributed evenly between the 2 products. The species produced have no charge and are called free radicals. They are very reactive.
Heterolytic Fission - this is when there is an uneven sharing of the electrons and both of them go to one partner from the bond to from ions
Substitution - a reaction in which one atom or group in a molecule is replaced by another, usually there are 2 starting molecules and 2 products.
Addition - 2 molecules add together to give a single product
Elimination - a reaction in which a (small) molecule is removed from a larger one, where one starting material gives rise to 2 products
Nucleophile - an atom, molecule or ion which seeks out centres beaing a positive charge, it will always have an electron deficient site
Electrophile - an atom or molecule which seeks out centres which are electron rich (often in unsaturated systems) and is able to accept an electron pair in order to form a dative covalent bond at the site of attack.