An atom is composed of protons, electrons and neutrons. The entire mass of an atom is concentrated in the nucleus which is at the centre. The nucleus contains protons and neutrons which are collectively called as nucleons. Electrons revolve around the nucleus in circular orbits. Protons are positively charged particles, electrons are negatively charged and neutrons have no charge. In an atom the number of protons and electrons are equal. Thus an atom is electrically neutral in nature.
Discovery of a proton
Goldstein in the year 1886 found that the charge to mass ratio of the positive particles depend on the nature of the gas which is present in the discharge tube. This means that the charge to mass ratio (e/m) was different for different gases. He observed that the charge to mass ratio of the positive rays was highest in case of the hydrogen gas that was used in the discharge tube. This is mainly because hydrogen is the lightest atom so m will be the least hence e/m ratio will be highest in this case.
The particle in the positive rays in the discharge tube was named as proton. A proton can be produced when we remove an electron from the hydrogen atom.
H (hydrogen atom) → H+ (proton) + e– (electron)
Thus, it can be said that proton is a hydrogen ion (H+).
Characteristics of protons
Proton is a positively charged particle and has the following physical properties:
- Mass of proton – The mass of a proton is equal to that of the hydrogen atom. Hydrogen atom consists of one electron and one proton. As the mass of an electron is considered to be negligible therefore it can be said that the mass of hydrogen atom is equal to the mass of proton. The mass of a proton is 1840 times the mass of an electron.
Mass of proton = 1.676 × 10-27 kg = 1.676 × 10-24 g
- Charge of proton – The charge of a proton is equal to and opposite to that of an electron. Thus, it has a unit positive charge.
Charge on a proton = + 1.602 × 10-19 coulombs
The properties and discovery of a proton is briefly described in this article. For any further query call the mentor support team at Byju’s.