Electrons

Introduction

The basic constituent of all the matters in our nature is atoms. And atoms are composed of small components called subatomic particles. They are the basic constituents of atoms. Protons, neutrons, and electrons are the 3 subatomic particles. The nucleus is the one that possesses the total mass of atoms.

A nucleus is composed of two subatomic particles: neutrons and protons. So, the subatomic particle electrons are massless species. Numerous experiments and theories proposed by scientists lead to the discovery of these subatomic particles. Several years ago, it was considered that an atom is an indivisible constituent of matter. In the year 1897 electrons were discovered by the experiments done by the physicist J.J. Thomson. The experiment he conducted for the discovery of electrons was the cathode ray discharge tube experiment.

An Introduction to Electrons

In an atom neutrons and protons are packed in a space called the nucleus which is buried in the cloud of electrons. Electrons present in an atom define the chemical and physical properties of every element and the compounds. Electrons are surrounding the nucleus in imaginary paths called shells or orbits. The arrangement of electrons around the nucleus is in a way that electrons with less energy are arranged near the nucleus and those with high energy are arranged at a higher distance from the nucleus. So high-energy electrons are present on the outer surface of atoms. And these electrons are also called valence electrons. The shells in which electrons are present are 𝐾, 𝐿, 𝑀, 𝑁, etc. And each shell can accommodate a particular number of electrons only. And the electrons accommodated by shells do not vary with different elements. In addition to this, there are subshells too. They are 𝑠, 𝑝, 𝑑, 𝑎𝑛𝑑 𝑓. And they also possess a particular number of electrons that they can accommodate. Electrons are inside in the order of energy levels. If an atom does not contain many electrons, it can have some empty shells and subshells. The flow of electrons in some elements is,

Thomson Cathode Ray Experiment

J.J. Thomson began his experiments in the cathode ray tubes in the late 19th century itself. Cathode ray tubes are glass materials that are completely evacuated. It is a tube that contains two electrodes at the two ends. A flow of particles will occur when a high voltage is supplied across this tube. The imaginary flow of particles originated from the cathode end. That is why it is called cathode ray. The ray produced is invisible, so it is detected with the help of a painting on the other side with a phosphorescent material. The rays are detected but their properties of it were not defined at the time. For understanding its properties, J.J. Thomson has placed two oppositely charged plates around the surface of the cathode.

It has been observed that the rays get deflected upon illuminating on the negative electric plate and get attracted towards the positive electric plate. So, he concluded that a particle arising from the cardboard material is negatively charged since the same charges repel each other. And then he also calculated the charge-to-mass ratio of the particles, but it is evident that it is much smaller than the mass of an atom. He also made the experiment by changing the metal as the electrode and it always repeated the same properties and observations. So, J.J Thomson then concluded after conducting this experiment. And are

• The particle that arises from the cathode is a negatively charged species.

• It is just a part of an atom since it does not have a mass. The mass was found to be $\mathrm{\frac{1}{2000}}$ to the mass of the hydrogen atom.

• These particles are present in all the elements.

The name electrons were provided to the cathode rays after the acceptance from other scientists. This experiment led to the discovery of the subatomic particle electron and it eliminated the theory that was put forward by Dalton in which atoms are indivisible particles. So, a new model of the atom is also mentioned after this experiment.

Define Electrons

Electrons are the negatively charged subatomic particle present in the atom. They are a stable species. The charge of an electron is 1.60 × 10−19𝐶. The mass of an electron is very small compared to the mass of an atom. And the mass of electrons is 9.11 × 10−31𝐾𝑔. Electrons are moving at a fraction of speed equal to the speed of light. The conductivity of metals over electricity is because of the presence of these electrons. In 1891 the scientist Stoney suggested the name electron to the negatively charged species. Electrons do not contain any further components. The properties of electrons do not vary with varying elements also. The characteristics of this subatomic particle are always unique.

Properties of Electrons

Some properties of electrons are tabulated below.

Electron	e-
Charge	Negative, $\mathrm{1.60\times\:10^{-19}\:C}$
Mass	$\mathrm{9.11\times\:10^{-31}\:Kg}$
Location	Present outside the nucleus of atoms.
Stability	Stable
Attraction	Towards positive charge species.

Electrons and Compound

The presence of valence electrons in elements is responsible for the formation of several chemical compounds. In elements, there is a particular number of electrons present in the outermost shell of them. Every element in nature aims to obtain stability by maintaining octets in their outermost shell. The sharing of electron pairs between elements results in the formation of covalent bonds and there forming a compound. For example, the outermost electron present in the oxygen atom is 6 and it in needs two more electrons to attain a stable configuration. So, when two oxygen atoms share the pair of electrons the compound or the molecule 𝑂2 is formed. So, in this way electrons help in the formation of a chemical compound.

Conclusion

Electrons are one of the important components of an atom. They are negatively charged massless particles present in the atom. It is revolving around the nucleus in an imaginary path called the shells or orbits. There is also a subcategory for these shells and subshells. They can carry a particular number of electrons only. Electrons are discovered by the experiment conducted by the scientist JJ Thomson in his cathode ray discharge tube experiment. Their discovery made him accepted by many scientists and proved that it is a massless species. The presence of electrons in the outermost shell of all the elements is responsible for the formation of a chemical compound. As compounds are formed by the sharing of electrons.

FAQs

1. Give the plum pudding model of the atom by J.J. Thomson?

After the discovery of electrons, concluded that atoms are almost neutral so they must contain some amount of positively charged species or protons. He proposed a model for an atom in which the electrons are embedded in the sphere of positive charge. It is like plum pudding hence it's named the plum pudding model. But it is not the correct model of an atom.

2. Who made the correct model of an atom?

The α-particle scattering experiments conducted by Rutherford made a proper explanation for the model of atoms. Through his experiment, it is proven that electrons present in an atom is revolving around the nucleus and there is a small space in the atom where all the mass is concentrated. This is an accepted model of atoms even though it also has some limitations.

3. Who discovered neutrons?

The sub-atomic particle that has a neutral charge in the atoms was discovered by the scientist, Chadwick in the year 1932.

4. Who discovered protons?

In the year 1900 proton was discovered by the scientist Ernest Rutherford. And is discovered through his gold foil experiment.

5. What is the electron theory?

According to electron theory, all the matter present in our nature is composed of molecules, each molecule present in our nature is composed of atoms, and each atom is composed of particles such as protons, neutrons, and electrons.