Class 9th – STRUCTURE OF ATOM (Subatomic Particles)

We have already discussed in the chapter of atoms and molecules, how atoms are made and how molecules are made.

In this chapter we will study in detail about the structure of Atom.

An atom is made up of 3 sub-atomic particles;

1. Protons.
2. Electrons.
3. Neutrons.

PROTONS

The discovery of proton was done by E. Goldstein.

OBSERVATION: At positive electrode the steams were given out and the steam was known as Anode Ray.

The positive electrode is called anode. thus, anode ray have positive particles and thus it resulted in the discovery of protons.

Protons can be defined as the positive charged particle found in the atoms of an element.

Protons are located in the Nucleus of an atom. The symbol of proton is p

The charge carried by a proton is 1.6 x 10^-19 C.

ELECTRONS

The discovery of electron was done by J.J THOMSON. He performed an experiment, where he passed electricity at high voltage at very low pressure through the gas in the discharge tube.

OBSERVATION: The streams were given out of the Negative Electrode. The negative electrode is called CATHODE, thus the discharge of stream is called CATHODE RAY.

The Electron is negatively charged particle present on the atom of an element. The symbol of electron is e. The charge of an electron is 1.6 x 10^-19 C.

NEUTRON

Neutron was discovered by James Chadwick. Neutron is present inside the Nucleus of an atom. The symbol is n and the charge of the neutron is Zero.