Discovery of Electron

A subatomic particle that is negatively charged was discovered by J.J. Thomson while experimenting with cathode-ray tubes which represented that all atoms have it within them. This discovery demonstrated that a 2000-year-old concept of an atom being a homogeneous substance was not correct, whereas it has a complex structure. Sealed glass tubes from which air is already vacuumed is known as cathode ray tube. The cathode ray experiment helped with the discovery of electrons.

Discovery of Electron

The experiment was done on a cathode ray tube, on which high voltage is applied to the two electrodes which are at one end of the cathode ray tube, which emits particles to circulate from the negatively charged electrode known as a cathode to a positively charged electrode called an anode. The tube is known as a cathode ray tube because of the particles emitted from the cathode. The ray is detected by painting phosphors on the far end of the cathode ray tube behind the anode. Phosphors emit light when it is embedded by the beam of particles.

In order to test the properties of particles, J.J. Thomson planted one positively charged and one negatively charged plate around the beam of particles. The beam gets diverted towards the positively charged plate and away from the negatively charged plate. This showcased that the beam is composed of particles that are negatively charged. Two magnets were also placed on the two sides of the tubes which demonstrated that the magnetic field also deviated from the cathode ray. This led to the discovery that the mass of every particle was less than that of an atom. He continued the experiment using several types of metals in the form of electrode materials and found out that the properties remained constant. This proved and concluded a few things such as:

• The beam of particles or cathode rays has negatively charged particles,
• The particle must be present as a part of an atom.
• We can find the subatomic particles within atoms of all kinds of elements.

This led to the discovery of electrons. Gradually J.J. Thomson’s theory was approved by scientists.

Discovery of Proton and Neutron

We will talk about the discovery of electrons, protons and neutrons.

Proton is also a subatomic particle that is positively charged. In 1886, E. Goldstein founded anode rays and demonstrated that it has positively charged subatomic particles. It was named protons by E. Goldstein which was derived from the Greek word protos which means first. The core of an atom was founded by Ernest Ruther in the famous gold foil experiment. It was concluded by him that the positively charged particles were condensed in a particular core and most of the atom’s volume was null. He also stated that the positively charged particles are in equal numbers to the negatively charged particle.

Rutherford already discovered, atomic nucleus in 1911 and protons in 1919, however it was noticed that there is something in addition to protons in the nucleus. For example, Helium has an atomic number of 2 but the mass is 4, according to some scientists there were additional protons but Rutherford stated that electrons and protons could combine and form a new particle to balance the additional charge but there was no solid evidence for that. He even stated that it will be difficult to detect the other particle.

This is how after many experiments’ atom was divided into three different particles which are termed as electron, neutron and proton. Hence the discovery of electrons, neutrons and protons were made by a number of scientists and it was a long procedure.

Conclusion

Hence one may conclude by saying that Dalton’s Atomic theory was termed wrong and had several drawbacks after the discovery of electrons, protons and neutrons. Especially after the discovery of Electron by J.J. Thomson. Atoms can be deconstructed into three particles: Positively charged protons, negatively charged electrons and neutral neutrons. The core of an atom consists of both protons and neutrons.