1.1: Know the terms ‘atom', 'element', 'ion', 'molecule', 'compound', 'empirical formula' and 'molecular formula’

Definitions:

• Atom: An atom is the smallest part of an element that can take part in a chemical reaction.
• Element: An element is a substance that cannot be broken down by chemical means into other substances.
• Ion: An ion is formed when an atom gains or loses one or more electrons. Ions are charged particles. Ionic compounds are formed from ions.
• Molecule: A molecule is the smallest part of a covalent compound or element that can exist on its own.
• Compound: A compound is formed when two or more different elements are chemically bonded together.
• Empirical Formula: This gives the simplest ratio of atoms of each element in a compound.
• Molecular Formula: This gives the actual number of atoms of each element in a compound.