Atoms:The basic building blocks of matter

Structure of an Atom:

Protons (+) → in the nucleus

Neutrons (no charge) → in the nucleus

Electrons (-) → move around the nucleus

Elements:

Pure substances made of only one type of atom, e.g., Gold (Au), Oxygen (O2)

Molecules:

Two or more atoms chemically bonded, e.g., Water (H2O), Table salt (NaCl)

Ions:

Atoms or groups of atoms that have gained or lost electrons

Positive ions (cations) → lost electrons

Negative ions (anions) → gained electrons