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# atomic structure-

## 1-charged particles in matter

By the 19th century it became clear that the atom was not indivisible. Rather the charged particle in the atom i.e. subatomic particle (sub atomic particles) are present.

The atom is made up of three subatomic particles, these particles are: electrons, protons and neutrons. all these atomic particles [(Sub Atomic Particles(अवपरमाणुक कण)] are called.

## 2-subatomic particles [सब एटॉमिक कण(Sub Atomic Particles)]

Electron : Electron is denoted by the English letter ee. The electron has a negative charge and is assumed to be zero due to the very small mass of the electron. Since the electron has a negative charge, it is denoted by e−e-.

Symbol of electron: e−e-

Mass of electron : 9.109×10−319.109×10-31

Relative mass of electron : 11836≈011836≈0 [चूँकि इलेक्ट्रॉन का द्रव्यमान काफी कम है, अत: इसे नगण्य मानकर शून्य माना जाता है। ]

Charge on Electron : The absolute charge on the electron is =−1.6×10−19=-1.6×10-19.

Relative charge on electron : −1-1

Location of the electron: In the orbits of the atom

## 3-electron discovery

Jo Jo Thomson, a British physicist discovered the electron in the year 1897. He stated that the atom has at least one negatively charged particle, which he named “corpuscles”. It was later named Electron.

Proton : Proton is denoted by the English letter pp. The proton has a positive charge and the relative mass of the proton is equal to 1. Since the proton has a positive charge, the proton is denoted by p+p+.

Sign of Proton: p+p+

Mass of proton : 1.673×10−271.673×10-27 kg

Relative mass of proton : 11

Charge on proton : Evasolute charge on electron is =1.6×10−19=1.6×10-19 Coulomb.

Relative charge on proton : +1+1

Location of Proton : In the nucleus of the atom

## 4-proton discovery

EO Goldstein, in the year 1886, even before the atom was discovered, discovered a new radiation, which he called the “canal ray”. These “canal rays” were positively charged rays, from which the proton was later named. The charge of these particles was equal but opposite to that of the electron. Their mass is about 2000 times greater than that of electrons.

Neutron: Neutron is denoted by the English letter nn. The neutron has no charge and the relative mass of the neutron is equal to 1.

Sign of Neutron: nn

Mass of Neutron : 1.673×10−271.673×10-27 kg

Relative mass of neutron : 11

Charge on Neutron: The avalute charge on the electron is 00 coulomb.

Relative charge on neutron : 00

Location of neutrons: in the nucleus of an atom

## 5-neutron discovery

Joe Chadwick, in the year 1932, discovered another sub-atomic particle. Since this sub-atomic particle had no charge, that is, was neutral, hence it was named neutron. The discovery of the neutron was made much after the discovery of the electron and the proton. The mass of the neutron is equal to the mass of the proton, and it resides in the nucleus of the atom.

## 6-Atom without neutron – Hydrogen

Atoms of all elements are made up of electrons, protons and neutrons, in other words electrons, protons and neutrons are present in all atoms. These particles are called subatomic particles or subatomic particles. In all these three atomic particles, protons and neutrons are in the nucleus of the atom and electrons revolve around this nucleus. But hydrogen is the only element that does not have neutrons. The hydrogen atom has only a proton in its nucleus, and an electron outside it, no neutron.

## 7-Atomic Structure

After the discovery of the electron and the proton, Dalton’s atomic theory, according to which the atom was indivisible and indestructible, was proved wrong. After this, many models were presented about the structure and arrangement of electrons and protons inside the atom.

Jo Jo Thomson was the first scientist, who presented the first model related to atomic structure.

Question 1. What are Canal rays?

Answer- Canal rays are positively charged radiation, which, when given voltage, travels from the anode to the cathode. These rays consist of positively charged particles called protons. It was discovered by E. Goldstein in 1886.

Question 2. If an atom has one electron and one proton, will it have any charge or not?

Answer-An electron is a negatively charged particle and a proton is a positively charged particle. Both the particles have equal charge. So if an atom has one electron and one proton, then it will have no charge. Thus it will be a neutral atom.

Question 3. On the basis of Thomson’s model, explain the fact that the atom is neutral.

Answer- The model of atomic structure that Thomson proposed was that of a positively charged sphere with electrons embedded in it like a watermelon seed. According to this model, the positive sphere negative and the positive charge are equal in magnitude, so the atoms are electrically neutral.

Question 4. According to Rutherford’s atomic model, which subatomic particle is present in the nucleus of an atom?

Answer- According to Rutherford’s atomic model, the nucleus of an atom is positively charged. Almost all the mass of an atom is contained in the nucleus around which electrons revolve in fixed orbits. These positively charged subatomic particles are protons.