chemistry topic one (AS1)

Avogadro’s number Number of atoms in 12.000g of carbon-12.

Mole The amount of substance which contains the Avogadro constant of atoms,

molecules or groups of ions.

Molar mass The mass of one mole of a substance.

Anhydrous A salt which contains no water of crystallisation.

Hydrated A salt which contains water of crystallisation.

Water of crystallisation Water chemically bonded within a crystal structure.

Atomic number The number of protons in an atom.

Mass number The total number of protons and neutrons in an atom.

Relative Atomic Mass

(RAM)

The average mass of an atom of an element relative to one-twelfth of the

mass of an atom of carbon-12.

Relative isotopic mass

(RIM)

The average mass of an isotope of an element relative to one-twelfth of the

mass of an atom of carbon-12.

Isotopes Atoms which have the same atomic number but have a different mass

number (contain the same number of protons but a different number of

neutrons).

Relative formula mass

(RFM)

The average mass of a formula unit relative to one-twelfth of the mass of an

atom of carbon-12.

Relative molecular mass

(RMM)

The average mass of a molecule relative to one-twelfth of the mass of an

atom of carbon-12.