AS level definitions

orbitals

a region around the nucleus that can hold up to two electron with opposite spins

covalent bond

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonding atoms

ionic bond

the strong electrostatic attraction between oppositely charged ions

electronegativity

an atoms ability to attract the electron pair in a covalent bond

avarage bond entahlpy

the energy required to break one mole of a specified type of bind in a gaseous molecule

firs ionisation energy

the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions

hess’s law

if a reaction can take place by two routes and the starting and finishing conditions are the same, the total enthalpy change is the same for each route

metallic bonding

the strong electrostatic attraction between positively charged metal ions and a see of delocalised electrons

enthalpy change of reaction

the enthalpy change that accompanies a reaction with the molar quantities shown in a chemical equation under standard conditions

standard enthalpy change of formation

the enthalpy change that takes place when one mole of a compound is formed from its elements under standard conditions with all reactants and their products in their standard states

enthalpy change of combustion

the enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions with all reactants and products in their standard states

enthalpy change of neutralisation

the enthalpy change that accompanies the reaction of an acid by a base to form one mole of H2O (l) under standard conditions with all reactants and products in their standard states

average bond enthalpy

the energy required to break one mole of a specified type of bond in a gaseous molecule