Nuclei part 02

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Nuclei part 02

Discovery of neutron

It is found that when Berrylium was bombarded by Alpha-particles, no protons were ejected as expected instead a highly penetrating type of radiation was emitted they assumed this radiation to be Gaama-rays, but these radiation could knockout protons from paraffin wax finally Chadwick performed an experiment. 



Radioactivity

The phenomenon of spontaneous disintegration of the nucleus of an atom with the emission of some radiations is called radioactivity. 

There are a no. Of heach elements occurring in nature whose nuclei are unstable and undergo spontaneous disintegration with emission of some radiations. 
Ex - alpha-rays, Beta-rays and Gaama-rays

There are few radiations emitting from radioactive materials Ex - alpha-rays, beta-rays and Gaama-rays. 

Properties of alpha-rays

(1). Alpha-rays are represented by helium atom. 
(2). Charge of an alpha = 2e
(3). The speed of alpha particles is about 10(of power of 7) m/s
(4). Penetrating npower of alpha rays is about 1/100 times of the beta rays. 
(5). Alpha particles are deflected towards negative polarity of applied E.F.
(6). Alpha particles affect the photographic plate. 
(7). Alpha particles have greatest ionisation efficiency. 

Properties of beta-rays

(1). It is represented by electron. 
(2). Charge on beta particles is electron. 
(3). Speed of beta rays is about 10(of power of 8) m/s but varying. 
(4). Beta-rays have penetrating power more than alpha particles. 
(5). Beta particles are deflected towards positive polarity of applied E. F. 
(6). Beta-rays affect photographic plate but in less manner than alpha-rays. 
(7). The Ionising efficiency of beta-rays is less than alpha-rays. 

Properties of Gaama rays

(1). It is represented by photons having fixed amount of energy. 
(2). Gaama-rays have zero charge. 
(3). Rest mass of Gaama-rays is zero. 
(4). Speed of Gaama-rays is equal to speed of light. 
(5). Penetrating power of Gaama-rays is very large. 
(6). Gaama-rays do not deflect in M.F and E.F.
(7). Gaama-rays do not affect photographic plate. 
(8). Ionising power is very small. 

Soddy - Fajan's law

It states that the total electric charge and mass no. Remains conserved after and before the disintegration of radioactive material. 

Some Features

When alpha particles emit from radioactive substance then mass no. Decreases by 4 and atomic no. Decreases by 2.





When beta particles emit from radioactive substance the mass no. Remains unchanged but atomic no. Increases by one. 



On emission of Gaama particles, both A and Z remain unchanged. 



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