Physical Definitions

ionisation energy

the energy required to remove one electron from every atom in one mole of gaseous atoms of an element

electronegativity

ability of an atom to attract a pair of electrons towards itself in a covalent bond

standard molar enthalpy of formation

the enthalpy change when one mole of substance is formed from its constituent elements under standard conditions, all reactants and products being in their standard states

empirical formula

simplest whole number ratio of atoms of each element in a compound

molecular formula

actual number of atoms of each element in a compound

standard enthalpy change of neutralisation

enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water

standard enthalpy change of combustion

the enthalpy change when one mole of substance is completely burned in oxygen under standard conditions, all reactants and products being in their standard states

enthalpy change

heat energy change at constant pressure

relative atomic mass

the average mass of an atom of an element relative to 1/12 the mass of a carbon 12 atom

relative molecular mass

average mass of one molecule relative to 1/12 of the mass of a carbon-12 atom

Hess’s law

the enthalpy change of a reaction is independent to the reaction route

first ionisation energy

energy needed to remove one mole of electrons from one mole of atoms in the gaseous state

rate of reaction

amount of substance formed or used up in a given time

calorimetry

measurement of enthalpy changes in a chemical reaction

Bronsted-Lowry acid

a proton donor

Bronsted Lowry base

proton acceptor

nucelophile

lone pair donor

electrophile

lone pair acceptor

entropy

measure of disorder in a system

first electron affinity

The standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single negative charge.

first ionisation energy

standard enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single positive charge

lattice enthalpy of formation

The standard enthalpy change when one mole of solid ionic compound is formed from its gaseous ions

enthalpy of lattice dissociation

The standard enthalpy change when one mole of solid ionic compound dissociates into its gaseous ions

enthalpy of hydration

The standard enthalpy change when one mole of gaseous ions is converted into aqueous ions

enthalpy of solution

The standard enthalpy change when one mole of solute dissolves completely in sufficient solvent to form a solution in which the molecules or ions are far enough apart not to interact with each other.

bond enthalpy

the energy required to break one mole of the specific bond forming gaseous atoms, under standard conditions averaged over a range of compounds

periodicity

repeating pattern of physical or chemical properties going across a period