Which of the following pairs is an isobar 

(1) ${}_1\mathrm{H}_1$ and ${}_1\mathrm{H}_2$               

(2) ${}_1\mathrm{H}_2$ and ${}_1\mathrm{H}_3$

(3) ${}_6\mathrm{C}_{12}$ and ${}_6\mathrm{C}_{13}$              

(4) ${}_{15}\mathrm{P}_{30}$ and ${}_{14}\mathrm{Si}_{30}$

Equivalent energy of mass equal to 1 a.m.u. is

(1) 931 KeV               

(2) 931 eV

(3) 931 MeV               

(4) 9.31 MeV

The mass number of a nucleus is equal to the number of

(1) Electrons it contains           

(2) Protons it contains

(3) Neutrons it contains           

(4) Nucleons it contains

In ${}_{88}\mathrm{Ra}_{226}$ nucleus, there are 
(1) 138 protons and 88 neutrons

(2) 138 neutrons and 88 protons

(3) 226 protons and 88 electrons

(4) 226 neutrons and 138 electrons

Outside a nucleus 

1. Neutron is stable

2. Proton and neutron both are stable

3. Neutron is unstable

4. Neither neutron nor proton is stable

Order of magnitude of density of uranium nucleus is (${\mathrm{m}}_{\mathrm{P}}=1.67\times {10}^{-27} \mathrm{kg}$)
(1) ${10}^{20} \mathrm{kg}/{\mathrm{m}}^3$           

(2) ${10}^{17} \mathrm{kg}/{\mathrm{m}}^3$

(3) ${10}^{14} \mathrm{kg}/{\mathrm{m}}^3$           

(4) ${10}^{11} \mathrm{kg}/{\mathrm{m}}^3$

Nucleus of an atom whose atomic mass is 24 consists of

(1) 11 electrons, 11 protons and 13 neutrons

(2) 11 electrons, 13 protons and 11 neutrons

(3) 11 protons and 13 neutrons

(4) 11 protons and 13 electrons

The mass of a neutron is very nearly the same as that of 

(1) A proton                 

(2) A meson

(3) An epsilon               

(4) An electron

The mass defect per nucleon is called

(1) Binding energy             

(2) Packing fraction

(3) Ionisation energy         

(4) Excitation energy