1. CHEMSS1 LESSON NOTE 4 PARTICULATE NATURE OF MATTER Matter is made up of discrete particles. The main ones are atoms, molecules and ions. ATOM:- An atom is the smallest particle of an element which takes part in chemical reaction. MOLECULE:- Molecule is defined as the simplest particle of a substance that exist alone and still retain the properties of that substance be it an element or a compound i.e there are molecules of the same element e.g O 2, Cl 2, H 2 or different elements e.g HCl, H 2 O, NaCl etc ATOMICITY Atomicity of a molecule is the number of atom present in one molecule of a substance e.g

2. Elements Atomicity Name Helium He 1 monoatomic Neon Ne 1 monoatomic Argon Ar 1 monoatomic Hydrogen H 2 2 diatomic Oxygen O 2 2 diatomic Nitrogen N 2 2 diatomic Chlorine Cl 2 2 diatomic Ozone O 3 2 triatomic phosphorus P 4 4 polyatomic Sulphur S 8 8 Polyatomic

3. IONS:- An ion is any atom or group of atom which possess electric charge ASSINMENT: List the first twenty elements and give their symbols