1. SPECIAL MOLECULES

2. Diatomic Molecules
Atoms that join together with other atoms form MOLECULES.
If there is only ONE type of atom it is a molecular element or Diatomic Molecule (prefix di means two)
There are 7 elements that for molecules consisting of two atoms:

3. H2 HYDROGEN
O2 OXYGEN
F2 FLUORINE
Br2 BROMINE
I2 IODINE
N2 NITROGEN
Cl2 CHLORINE
Most molecules contain more than one type of element. These molecules are called MOLECULAR COMPOUNDS.

4. Polyatomic Ions
Tightly bound groups of atoms that behave as a single unit and have ONE charge
When two or more non-metal atoms bond to each other, they do so by sharing electrons.
Sometime even after sharing electrons, the collection of atoms needs even more electrons than what it can get by sharing

5. Common Polyatomic Ions

6. Examples
Al(OH)3
KHCO3
Na(NO3)
CaSO4
Li3(PO4)
Mg(ClO3)2
KCN