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.
|Sodium bicarbonate (baking soda)||NaHCO3|
|Sodium chloride (table salt)||NaCl|