What are Protons?
Protons are sub-atomic particles having a positive charge and are present in the nucleus of the atom.
Dalton’s atomic theory was able to explain the law of conservation of mass, the law of constant composition and the law of multiple proportions very successfully. However, it failed to explain the results of many experiments; for example, it was known that substances like glass or ebonite when rubbed with silk or fur generate electricity. Many different kinds of sub-atomic particles were discovered in the twentieth century. However, in this section, we will talk about three particles, namely electron, proton and neutron.
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Discovery of Protons
We know that an atom is electrically neutral, if it contains negatively charged electrons it must also contain some positively charged particles. This was confirmed by Goldstein in his discharge tube experiment with the perforated cathode. On passing high voltage between the electrodes of a discharge tube it was found that some rays were coming from the side of the anode which passed through the holes in the cathode. These anode rays (canal rays) consisted of positively charged particles formed by the ionization of gas molecules by the cathode rays. The charge-to-mass ratio (e/m value) of positively charged particles was found to be maximum when the discharge tube was filled with hydrogen gas as hydrogen is the lightest element. e/m varies with the nature of the gas taken in the discharge tube. The positive particles are positive residues of the gas left when the gas is ionized.
Mass of Proton
The mass of the proton in kg is = 1.673´10–27
| Electron | Proton | Neutron | |
|---|---|---|---|
| Approximate relative mass | 1/1836 | 1 | 1 |
| Approximate relative charge | –1 | +1 | No charge |
| Mass in kg | 9.109´10–31 | 1.673´10–27 | 1.675´10–27 |