# Electrons - The Sub-Atomic Particles

Electrons – The Sub-atomic Particles

An atom is the smallest unit of matter. Maharishi Kanada was the first scientist who came up with the concept of divisibility of matter and named the smallest unit as paramanu. Later, scientists discovered the fundamental sub-atomic particles protons, electrons, and neutrons. An atom has a bulk mass at its centre called as a nucleus. The nucleus contains the protons and the neutrons. Considering the solar system, it has been observed that the sun is at its centre, and the planets revolve around it. Similarly, in an atom, the nucleus is at the centre, and the electrons revolve around the nucleus.

Source: Wikipedia

The above image clearly shows the structure of an atom and its similarity with the structure of the solar system. The planets in the case of solar system or electrons in the event if an atom revolves around the sun and the nucleus respectively.

The credit for the discovery of electron goes to J.J. Thompson.  He performed an experiment on the cathode rays; he showed that the cathode rays are charged particles. The velocity of cathode rays was much less as compared to the speed of light. He devised methods to measure the charge to mass ratio of cathode rays. Thompson therefore concluded that the cathode rays is $\frac {1}{1000^{th}}$ mass of hydrogen ion (which is a proton). These negatively charged cathode ray particles are now known as electrons.

Electrons are negatively charged particle with negligible mass. The mass of an atom is the sum of the number of protons and neutrons. Protons are positively charged particles whereas neutrons do not carry any charge. The number of protons and electrons is equal hence an atom is electrically neutral in nature. Protons and neutrons together are known as nucleons.

### The charge of electrons

An electron is a negatively charged particle. The negative charge is equal to 1.602 × 10-19 coulomb in magnitude. The mass of an electron is $\frac {1}{1837}$ of a proton.

This article contains the basic properties of electrons. For any further query call the mentor support team at Byju’s.

#### Practise This Question

Which fundamental particle is not present in the nucleus of a hydrogen atom?