[Chemistry Class Notes] on Subatomic Particles Pdf for Exam

The name “atom” is derived from the Greek word “a-tomio,” which means “uncuttable” or “non-divisible.” For the longest period, scientists assumed that atoms were indestructible. 

However, some scientists discovered in the early twentieth century that atoms may be broken down further into smaller components such as electrons, protons, and neutrons. Subatomic particles are what they’re called.

Discovery

The rules of conservation of mass, constant composition, and various proportions were all satisfactorily explained by Dalton’s atomic theory. 

However, it was unable to account for certain other facts, such as the creation of electricity on rubbing glass or ebonite when silk or fur was used. 

These findings paved the way for the discovery of subatomic particles in the twentieth century. Let’s take a look at how the three subatomic particles were discovered.

Discovery of Electron

Electrons are subatomic particles. It spins around an atom’s nucleus. When electrons are lost or gained from an atom, ions are created. Chemical bonding occurs when electrons from different atoms join together. A few points about the discovery of electrons and their properties are listed below:

• J. Thompson is credited with discovering electrons since he was the first to precisely calculate an electron’s mass and charge.

• All elements have an equal number of electrons and protons in their atoms.

• When compared to the mass of a proton, the mass of an electron is insignificant. Its mass is discovered to be 1/1837 times that of a proton.

• An electron has a charge of -1.602 * 10-19 Coulombs.

• Electrons are negatively charged subatomic particles.

Discovery of Proton

Positively charged particles, sometimes known as canal rays, were discovered as a result of the cathode ray tube experiment. The following are their characteristics:

• The charge-to-mass ratio of these particles varies depending on the gas they come from.

• A multiple of the fundamental unit of electrical charge is carried by some positively charged particles.

• In an electrical or magnetic environment, these particles behave in the opposite way as cathode rays.

In 1919, this was characterised and the lightest and smallest positively charged particle made from hydrogen came into existence known as Proton. 

Discovery of Neutron

Later on, scientists found an electrically neutral atom component. Chadwick, a scientist, did an experiment in which he bombarded a thin sheet of beryllium with particles in 1932. He saw the emission of electrically neutral particles that were slightly heavier than protons. As a result, these particles were given the name neutrons.