MOLAR MASS

The molar mass of a substance is its relative molecular mass expressed in grams per mole.

RELATIVE ATOMIC MASS

The relative atomic mass of an element or compound is the number of times the average mass of one atom of that element is heavier than one-twelfth the mass of one atom of carbon-12.

RELATIVE MOLECULAR MASS

The relative molecular mass of an element or compound, is the number of times the average mass of one molecule of it is heavier than one-twelfth the mass of one atom of carbon-12.

The relative molecular mass of an element, is the sum of the relative atomic masses of all the atoms in one molecule of that substance. It is also referred to as the formula mass, this is a more general term.

Note that the relative molecular mass refers only to the relative mass of a molecule.  The formula mass refers not only to the relative mass of a molecule,  but also that of an ion, radical,  electron or any other specified groups or nuclear particles.

RADICALS

A radical is a group of atoms that functions as a single unit in chemical reactions.

PARTICULATE NATURE OF MATTER

Matter is made up of discrete particles, the most widely known ones being atoms, molecules and ions.

WHAT IS AN ION?

An ion is an atom or group of atoms which possess an electric charge.

There are two types of ions: the positively charged ion known as cations, and the negatively charged ions known as anions.

Ions are represented by formulae.

ATOMICITY OF AN ELEMENT

The atomicity of an element is the number of atoms in each molecule of an element.

This number is usually small. Example is in oxygen and chlorine, they are diatomic, meaning their molecules have two atoms, and sulphur and phosphorus exists as polyatomic molecules.