Discovery of Electron

Introduction

Electrons $\mathrm{([e^{-})]}$ are atom particles, just as atoms are matter substructures. These atoms can't be formed or destroyed. Until the discovery of electrons $\mathrm{([e^{-})]}$ atoms was thought to be the smallest unit of a particle. Some of the fundamental properties of atoms were revealed by the tests employed in the discovery of the electron $\mathrm{([e^{-})]}$ . Because the electron $\mathrm{([e^{-})]}$ was the first subatomic particle found, it is regarded as a watershed moment in physics. It turned out to be 1 of the most essential for describing the chemical bond in today's chemistry as well as physics.

Thomson Cathode Ray Experiment

In the early nineties, physicist J.J. Thomson (J.J.T.) conducted research on cathode ray tubes (CRT). There is a vacuum-sealed glass tube. A large voltage is applied across 2 electrodes on 1 side of the tube, leading a stream of particulates to move from the cathode to the anode.

Since the particle beam originates at the cathode, the tubes are known as cathode-ray tubes (CRT). When the beam strikes the phosphors, they spark or emit light. He (Thomson) explored the characteristics of the particles by encircling the beam with 2 oppositely charged electric plates. The beam was diverted from the negatively charged to the positively charged electric plate. Per this, the beam was composed of negatively charged particles.

He also placed 2 magnets on either side of the tube as well as discovered that the magnetic field redirected the beam. He used the findings of these tests to calculate the mass-to-charge proportion of beam particles, which led to an experiment that reveals that: an individual particle's mass was significantly less than that of any known atom. He carried out more tests with metallic elements as electrode components & observed that the Cathode Ray (CR) qualities were identical as well as independent of cathode substance.

Based on the facts, the following conclusions were made −

• The cathode ray is made of negatively charged components.

• Since each particle has a mass of 1 by 2000 times that of a 𝐻-atom, they must've been components of the atom.

• These subatomic particles may be detected in the atoms of all elements.

His findings were originally controversial, but experts gradually accepted them. This cathode ray (CR) particles were subsequently referred to as electrons $\mathrm{(e^{-})}$.

Define Electrons

The electron $\mathrm{(e^{-})}$ is a low-mass, negatively charged particle. Therefore, moving near to another e- or an atom's positive nucleus may easily deflect it. It was the 1𝑠𝑡 fundamental component found. They are subatomic particles having an elementary charge of -1. The charge of an $\mathrm{e^{-}}$ has a similar charge as of a proton (but has an opposite sign).

Electron Charge

Although protons, as well as $\mathrm{e^{-}}$ , have the same magnitude of charges, an electron's size as well as mass are much smaller than a proton. An $\mathrm{e^{-}}$ is a negatively charged particle. The -ve charge has a magnitude of 1.602 ✕10−19 Coulomb. An $\mathrm{e^{-}}$ has 1/1837 the mass of a proton.

Electron Mass

An electron $\mathrm{(e^{-})}$ has a mass of 9.10938356✕10−31 kilograms. The electron $\mathrm{(e^{-})}$ has a negligible mass in comparison to the proton.

Properties of Electrons

• Electrons are negatively charged particles that orbit an all-around nucleus, which consists of the proton as well as neutron at the centre of an atom.

• Electrons, unlike protons and neutrons, are the only basic constituents of an atom that cannot be further subdivided. They are denoted by the letters 𝑒 or 𝑒−.

• Electrons have varying energy levels and may be transported to higher energy levels by absorbing some energy.

• Electrons do not contribute to the overall mass of atoms since they have a negligible mass of 9.1094✕10−31 kg.

• An 𝑒− has an electric charge of -1, which is the inverse of a proton's charge of +1. Electrons move in a certain orbit around the nucleus due to the force of attraction between negatively charged electrons with positively charged protons.

Electrons and Compounds

In 1897, electrons were found. Nonetheless, the electron's meaning, as well as significance, were reinterpreted with the finding of the proton in the year 1911-1919 as well as the neutron in the year 1932. The discovery of the other 2 subatomic particles established the complete notion of atomic structure.

Protons are positively charged subatomic particles found in the nucleus of an atom. Electrons are 99.86 percent the size of protons, as well as the no. of protons in an atom varies by element. Hydrogen (𝐻), for example, has 1 proton, whereas oxygen (𝑂) has 8 and carbon (𝐶) has 6.

Neutrons were hypothesised by Rutherford when he found the proton, but they were found by Chadwick in 1932. Neutrons were subatomic particles with no neutral charge, thus their name. Except for the hydrogen (𝐻) atoms, all other elements in the periodic table are made up of neutrons. The mass of a neutron is somewhat more than that of a proton.

Conclusion

J.J. Thomson's findings were generally acknowledged, plus his cathode ray particles were dubbed electrons. His experiments led to the development of a new atomic model to better comprehend the structure of an atom. An American physicist called Robert Millikan established the charge of the electron. He calculated the charge on a single electron using electrically charged oil droplets. A single 𝑒− has a charge of 1.602 ✕10−19 Coulomb, as per him. Millikan computed the mass of an electron using J.J. Thomson's mass to charge ratio as well as the charge on a single 𝑒−. The electron has a mass of 9.1094✕10−31 kg. He won the Nobel Prize in Physics in 1906 for finding the basic particle electron.

FAQs

1. What was the situation inside J. J. Thomson's discharge tube when he discovered electrons or Cathode rays?

• It has to have a very low pressure of 0.01 mm Hg.

• It should be equipped with a vacuum.

• Across the terminals, a very high voltage should be supplied.

2. What effect does the electric field (E.F.) have on cathode rays?

• Because of the electric field (E.F.), cathode rays deviated from their straight-line route.

• Because of their -ve charge, they are drawn to the positive field and repelled from the -ve field.

3. Give 2 Cathode ray characteristics?

• They follow a straight line and are negatively charged.

• They can travel through matter as well as ionise the particles of the gases through which they travel

4. How are X-rays created?

When a cathode ray beam is directed towards hard metallic material such as tungsten (𝑊)X-rays are created.

5. What role did Faraday's investigation of static electricity have in the finding of subatomic particles?

Earlier, Dalton presented the atomic theory, which states that atoms are the most fundamental constituents of matter and thus are indivisible, but Faraday discovered that electricity flows through matter owing to charged particles when investigating static electricity. Much research even suggests that atoms can be divided into more fundamental particles. Thus, Faraday's investigation of static electricity prepared the path for the finding of subatomic particles.