Electrons

Let Us Learn About Electrons

Electrons are much smaller than neutrons and protons. The mass of a single neutron or proton is more than 1,800 times greater than the mass of an electron. An electron has a mass of 9.11 x 10^-28 grams.

Electrons have a negative electrical charge, with a magnitude which is sometimes called the elementary charge or fundamental charge. Thus an electron is said to have a charge of -1. Protons have a charge of the same strength but opposite polarity, +1. The fundamental charge has a strength of 1.602 x 10^-19 coulomb.

The electron (also called negatron, commonly represented as e⁻) is a subatomic particle. In an atom the electrons surround the nucleus of protons and neutrons in an electron configuration. The word electron is a transliteration of the Greek word ηλεκτρον, which means electrum, an alloy of silver and gold.

Electrons have an electrical charge and when they move, they generate an electric current. Because the electrons of an atom determine the way in which it interacts with other atoms, they play a fundamental part in chemistry.

An electron is defined as a subatomic particle which carries one unit of electrical charge (1.602 x 10^-19 C) and has a mass (9.1 x10 ^-28g).

The mass of an electron is almost negligible, being 1/1837^th the mass of an atom of hydrogen. The charge of an electron is referred to as unit negative charge and is the smallest known electrical charge.

The discharge tube experiments showed that irrespective of

• The gas used

• The nature of the material of the cathode, all electrons were found to have the same mass and same charge and therefore the same e/m ratios. Thus electrons of all cathode rays are the same and only electrons (no gaseous atoms) make up the fundamental common particles fo the rays.

It has been found that all electrons emitted from all sources and by all methods have the same mass and same charge. The electron in the atom is considered the universal constituent of all matter.

Charge and Mass of Electron

The charge to mass ratio is found by measuring the deflection of a ray under the simultaneous influence of electrical and magnetic fields, applied perpendicularly to each other as well as to the direction of the flow of light. This is illustrated in the figure below:

A high voltage charge accelerates cathode ray electrons between cathode and anode. After the anode, a circular disc selects a straight beam and directs it past the electric and magnetic fields, which are perpendicular to each other as well as to the direction of the motion of the light beam. The beam is deflected according to the relative strengths of the electric and magnetic fields and the ratio of e/m controls the deflection. By measuring the deflection and the field strengths of the two fields the e/m ratio can be calculated