Module 2: Foundations in Chemistry

Isotopes

Atoms of the same element with the same numbers of protons and electrons, different number of neutrons and different masses

Relative isotopic mass

Mass of an isotope compared with 1/12 of the mass of an atom of carbon-12

Relative atomic mass

Weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of carbon-12

Amount of substance

Number of particles in a substance, measured in moles (mol)

Mole ('mol')

The unit for amount of substance

1 mole

The same number of particles as there are atoms in exactly 12g of carbon-12

Avogadro constant

The number of particles per mol. NA = 6.02 x 1023 mo|1

Molar mass

Mass in grams per mole of a substance, units gmol-1

Molar gas volume

The volume of 1 moles of a gas units dm3 mol-1

Empirical formula

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

Molecular formula

The number of atoms of each element in a molecule

Anhydrous

Contains no water of crystallisation

Hydrated

Contains water molecules (water of crystallisation) as part of the crystalline

Water of crystallisation

The water molecules contained within a crystalline structure

Ideal gas equation

pV = nRT

Oxidation

Loss of electrons (increase in oxidation number)

Reduction

Gain of electrons (decrease in oxidation number)

Atomic orbital

Region around the nucleus that can hold up to two electrons, with opposite spin

Ionic bonding

The electrostatic attraction between positive and negative ions

Covalent bonding

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

Electronegativity

The ability of an atom to attract the bonding pair of electrons in a covalent bond