DISCOVERY OF NEUTRON

After the discovery of electron and proton Rutherford (1920) had predicted the existence of a neutral fundamental particle. In 1932, Chadwick bombarded the element Beryllium with a-particles and noticed the emission of a radiation having the following characteristics. 

  •  The radiation was highly penetrating.

  •  The radiation was unaffected by magnetic and electric fields which show that it is electrically neutral.

  •  It was found to have approximately the same mass as the protons. 

The name ‘neutron’ was given to this sub-atomic particle. It is denoted by n or 1on. Bombardment of beryllium by α-particles results in the formation of carbon and neutrons are emitted.

               α

        Be —   — → C + 1 n 
                                      0

At present there are a number of evidences which confirm that like electron, proton and neutron is also a fundamental constituent of atoms (a single exception is 11H atom which does not contain any neutron)

Mass of a neutron is 1.008930 amu (1.6753 x 10–24g or 1.6753 x 10–27 kg)

Neutron “A sub-atomic particle, which is a fundamental constituent of matter having mass approximately equal to the hydrogen atom and which is electrically neutral, is called a neutron”. 

Illustration:-The neutron is attracted towards

        (A)    Positive charged particles

        (B)    Negative charged particles

        (C)    Not attracted by any charge

        (D)    None of these

Solution: Neutron is an uncharged particle. Hence (C) is correct.   

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