The history of the atomic structure and quantum mechanics dates back to the times of Democritus, the man who first proposed that matter is composed of atoms. These theories could not gain much importance due to the lack of technology. John Dalton’s atomic theory was a stepping stone which revived the idea of atoms. For a long time, it was believed that atoms are the ultimate particles that make matter and it cannot be divided further. The experiments conducted during the latter part of the nineteenth century and early years of the twentieth century revealed that even atom is not the ultimate particle. The continued efforts of the scientists led to the discovery of subatomic particles. The limitations of Dalton’s atomic model to explain certain observations formed the basis for the discovery of protons and neutrons.
Discovery of Proton:
Who discovered proton?
Ernest Rutherford is credited with the discovery of proton in 1920. The experiments that led to the discovery of protons were based on electrical discharge in modified cathode ray tubes. The observations revealed that these particles (protons) were positively charged. The rays carrying positively charged particles are also known as canal rays. They are simply the positively charged gaseous ions. Some of the properties of protons are:
- The charge to mass ratio of the particles is found to depend on the gas from which they originate. Thus, the proton or the positively charged particles depend on the nature of gas present in the discharge tube.
- The photon or positively charged particles were found to exist carrying a multiple of the fundamental unit of electrical charge.
- The behavior of a proton in an electric or magnetic field is just opposite to that of an electron.
Discovery of Neutron:
Who discovered the neutron?
In the year 1932, James Chadwick discovered neutrons, another subatomic particle. He bombarded a thin sheet of beryllium by α-particles and found that electrically neutral particles with a mass slightly greater than that of the proton were being emitted. Chadwick called these particles as neutrons.
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