1.2: Compounds and Molecules
A molecule is formed when two or more atoms join together. A compound is formed when two or more different elements combine in a fixed ratio by mass. Note that some atoms are never found alone. For example oxygen is always found as molecules of 2 oxygen atoms (represented as O 2 ).
The table below gives some common compounds.
| Compound | Symbol |
|---|---|
| Calcium carbonate | CaCO 3 |
| Carbon dioxide | CO 2 |
| Copper sulphate | CuSO 4 |
| Glucose | C 6 H 12 O 6 |
| Hydrochloric acid | HCl |
| Sodium bicarbonate (baking soda) | NaHCO 3 |
| Sodium chloride (table salt) | NaCl |
| Sodium hydroxide | NaOH |
| Water | H 2 O |