Question

What do the following abbreviations stand for ?

1. O
2. 2O
3. O₂
4. 3O₂

Answer 1

1. O stands for an atom of oxygen.
2. 2O refers to two atoms of oxygen which are not chemically bonded.
3. O₂ refers to a molecule of oxygen in which atoms are chemically bonded to give a molecule of oxygen gas.
4. 3O₂ refers to three molecules of oxygen.