1. Introduction to structure of the atom

In our lower classes, we have studied about the atom. Let us recall them.

A series of experiments by scientists resulted in the discovery of an atom's structure.

 

According to Dalton, atoms are indivisible. Later on, one of the first indications is that atoms are not indivisible since there are smaller particles inside an atom.

 

According to Thomson, atoms are indivisible, but they contain at least one subatomic particle, the electron.

 

According to E. Goldstein, gas discharge contains new radiations known as canal rays. The rays had a positive charge. Canal rays helped the discovery of another subatomic particle. The charge of this subatomic particle was the exact opposite of the charge of the electron.

 

 

What are subatomic particles?

During the twentieth century, discoveries were made that atoms of all elements are made up of smaller components such as electrons, protons and neutrons.

 

 

Subatomic particles	Scientists name	Symbol	Charge	Mass (amu)
Electron	J. J. Thomson	\(e^-\)	\(-1\)	\( 0\)
Proton	Eugen Goldstein	\(p^+\)	\(+1\)	\(1\)
Neutron	James Chadwick	\(n^0\)	No charge	\(1\)

 

Neutrons are present in all atoms except hydrogen.

The sum of the masses of protons and neutrons in the nucleus defines the mass of an atom.

 

 

In this chapter, we will discuss about the topics listed below: