# Atomic Numbers and Atomic Weights.

## Atomic Numbers & Atomic Weights.

### Atomic Numbers & Atomic Weights.

The oxygen atom has 8 protons, 8 neutrons and 8 electrons. The atomic number of oxygen is the number of protons it has; so it is 8. Logically, the weight of the atom would be sum of the weights of the components.It is known that the protons and neutrons have almost the same weight. An electron, on the other hand, has (1/1837)th the weight of the proton. Hence, electrons do not contribute much to the weight of the atom.

Let us assume that the protons weight one unit. The neutron would also be of the same weight. If so, the weight of the oxygen atom will be the sum of the weights of 8 neutrons and 8 protons. That make the oxygen atom 16 units heavy. The

**atomic weight**of oxygen is therefore 16.

Hydrogen has 1 electron, 1 proton and 0 neutrons. Can you now tell the atomic number and atomic weight of hydrogen?