1.2: Compounds and Molecules
- Page ID
- 2172
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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 O2).
The table below gives some common compounds.
Compound | Symbol |
---|---|
Calcium carbonate | CaCO3 |
Carbon dioxide | CO2 |
Copper sulphate | CuSO4 |
Glucose | C6H12O6 |
Hydrochloric acid | HCl |
Sodium bicarbonate (baking soda) | NaHCO3 |
Sodium chloride (table salt) | NaCl |
Sodium hydroxide | NaOH |
Water | H2O |