What is an Electron

The centre of an atom, the nucleus, was discovered by a famous physicist Ernest Rutherford in 1911. The term nucleus came from the Latin nucleus, which means “kernel” or “core,” a miniature of nux (“nut”). Therefore, the nucleus is a small, dense, positively charged region at the centre of an atom.

The nucleus is the centre of an atom. An atom is the smallest particle of matter that cannot be bifurcated further. An atom constitutes two regions:-

1. The nucleus is in the centre of an atom and comprises positively charged protons and uncharged neutrons.
2. The outer region holds the negatively charged electrons that revolve in orbit around the nucleus.

Almost all the mass of an atom is concentrated in the nucleus since protons and neutrons have much more mass than electrons.

Definition of Electrons

An electron is a minute subatomic particle that can either be free (not attached to any atom) or bound to the nucleus of an atom and holds a negative charge.

Discovery of Electrons

Electron was discovered due to the investigation of cathode rays by British physicist J.J. Thomson in 1897.

The study on the existence and characteristics of these negatively charged particles was kickstarted by Julius Plucker in 1859 by the conduction of electricity through gases at external pressure in a discharge tube.

The discharge tube comprises a hard glass cylindrical tube with two metal electrodes sealed on both ends. 

When the air was eliminated from the discharge tube, and a side tube was connected to it to evacuate any desired pressure using a vacuum pump, and a high voltage of approximately 10,000 volts or more was passed across the electrodes, some invisible rays were observed moving from negative electrode to positive electrode. 

The negative electrode is called a cathode; hence these rays were known as Cathode rays.

After further observations by J.J. Thomson and other following properties of electrons came into the picture:

1. Electric and magnetic fields deflect the invisible rays. For example, when they are impressed between two electrically charged plates, these are deflected towards positively charged plates, showing that these cathode rays carry a negative charge.
2. They possess kinetic energy, which was observed by placing a small pinwheel in their path, leading to the wheel’s blades in motion. Thus, it was concluded that cathode rays consist of particles that have mass and velocity.
3. They travel straight lines away from the cathode with very high velocities.
4. These rays affect the photographic plate.
5. The character of cathode rays is independent of the following:

• The nature of cathode, and
• The gas in the discharge tube

These negatively charged particles were called negatrons by J.J. Thomson. Later, Stoney called these Negatron electrons.

What is an Electron?

An Electron is a minute subatomic particle carrying a negative charge of 1.6 x 10-19  C and a mass of 9.11 x 10-31 kg. It was discovered by J.J. Thomson in 1897.

Electrons exist in the volume of an atom that surrounds the nucleus. They exist in the spherical shells around the nucleus of an atom and depict multiple energy levels.

Larger spherical shell= Higher energy contained in the electron

An electron features a mass of roughly 1/1836 of the mass of a proton. The number of negatively charged electrons is the same as positively charged protons in an atom.

electrons(-1)= protons(+1)= atom charge-neutral

Electrons have no components or substructure. Therefore generally, they are considered to be elementary particles. The antiparticle of an electron is known as a positron.

In the case of electrical conductors, current flows due to the movement of electrons from atom to atom individually and from the negative pole to the positive pole in general. 

On the other hand, the flow of current in semiconductors can be due to the movement of electrons or due to the deficit of electrons. An electron-deficient atom in a semiconductor is known as a ‘hole’. Holes generally shift from positive to negative electric poles.

Conclusion

An atom, the smallest unit of matter, cannot be bifurcated further. Atoms contain a Nucleus, and the nucleus is composed of Nucleons (protons and neutrons) and electrons. Electrons— the negatively charged particles, revolve around the nucleus of an atom and remain attracted to the nucleus due to the positive charge.

Protons are positively charged particles fused with the neutrally charged neutrons and are present inside the atom’s nucleus. The number of negatively charged atoms is equal to the positively charged protons. 

The number of positively charged protons in the nucleus is equivalent to the atomic number (Z). The number of neutral or zero charged neutrons can be calculated by the difference between the atom’s mass number (M) and the atomic number (Z).