Question

(a) Write the name of the sub-atomic particle discovered by J. Chadwick. What type of charge occurs on this particle? In which part of atom this particle is located? 

(b) List three steps of experiment performed by Rutherford for his model of an atom. 

(c) Define isobars, write its one example. (d) Which scientist concluded that size of nucleus is very small as compared to size of an atom?

Answer 1

(a) Chadwick discovered neutron. Neutron is a neutral particle so it does not have any charge. It is located in nucleus of any atom. 

(b) (i)Most of the α -particles passed through the gold foil without any deflection. 

(ii) Some of the α - particles were deflected through small angles and a few deflected through large angles. 

(iii)Very few were deflected back, i.e. through an angle greater than 90°. 

(c) Atoms of different elements having same mass number but different atomic number are known as isobars. For e.g. ₂₀Ca ⁴⁰ and ₁₈Ar ⁴⁰ . 

(d) Rutherford concluded that size of nucleus is very small as compared to size of an atom