Module 2: Foundations in Chemistry

Isotopes: Atoms of the same element with the same numbers of protons and electrons,

different numbers 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. Contains 6.02 x1023 particles \[the Avogadro number of particles\]

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: g mol1

Molar gas volume: The volume of 1 moles of a gas. Units: dm? 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

structure.

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 the bonded atoms

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