The Discovery of the Proton
- The nuclear model was improved when the particles within the nucleus were discovered
- Ernest Rutherford discovered that the positively charged nucleus of all materials could be broken down into smaller positively charged particles
- The smallest of these parts had the same charge as a Hydrogen nucleus
- This amount of charge is called the elementary charge
- He called the positively charged particles in the nucleus as protons
- ‘Proto’ means original - protons are the original unit of positive charge
Worked example
An alpha particle is the nucleus of a Helium atom.Determine the charge of an alpha particle.
Step 1: Determine the number of protons in the particle
- The alpha particle has two protons
Step 2: Determine the number of electrons
- There are no electrons in the nucleus of an atom
- Since the alpha particle is a helium nucleus, it has no electrons
Step 3: Determine the charge of the alpha particle
- The total charge is the sum of the positive protons and negative electrons
- There are 2 protons and 0 electrons
2 – 0 = 2
- The charge on the alpha particle is +2