Structure of Nucleus

    Which of the following particles are constituents of the nucleus

• Protons and electrons  

• Protons and neutrons   

• Neutrons and electrons

• Neutrons and positrons

Answer explanation

The nucleus is made up of protons and neutrons. Electrons are found in the electron cloud surrounding the nucleus, while positrons are not constituents of the nucleus. Therefore, the correct answer is protons and neutrons.

   Nuclear binding energy is equivalent to

• Mass of proton        

• Mass of neutron          

• Mass of nucleus  

• Mass of defect of  nucleus

Answer explanation

Nuclear binding energy is the energy required to disassemble a nucleus into its constituent protons and neutrons. It is equivalent to the mass defect of the nucleus, which is the difference between the mass of the nucleus and the sum of its parts.

    If the binding energy of the deutrium is 2.23 MeV . The mass defect given in a.m.u. is

• -0.0024           

• -0.0012            

• 0.0012            

• 0.0024

Answer explanation

The mass defect can be calculated using the formula: mass defect (in a.m.u.) = binding energy (in MeV) / 931.5. Thus, 2.23 MeV / 931.5 MeV/a.m.u. = 0.0024 a.m.u. Therefore, the correct answer is 0.0024.

    Which of the following has the mass closet in value to that of the positron

• Proton           

• Electron    

• Photon              

• Neutino

Answer explanation

The positron has a mass similar to that of the electron, which is approximately 9.11 x 10^-31 kg. The proton and neutron are much heavier, while a photon has no mass. Therefore, the electron is the closest in mass to the positron.

The radius of a nucleus of a mass numb^er A is 

• A³          

• A    

• A^2/3                  

• A ^1/3                                         

Answer explanation

The radius of a nucleus is proportional to the cube root of its mass number A, which is expressed as A^(1/3). Therefore, the correct choice is A^(1/3).

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

• electrons it contains                       

• protons it contains   

• neutrons it contains                       

• nucleons it contains

Answer explanation

The mass number of a nucleus is the total number of nucleons, which includes both protons and neutrons. Therefore, the correct answer is that the mass number is equal to the number of nucleons it contains.

Atomic number of a nucleus is Z and atomic mass is M. The number of neutrons is

• M-Z

• M  

• Z  

• M+Z

Answer explanation

The number of neutrons in a nucleus is calculated by subtracting the atomic number (Z) from the atomic mass (M). Therefore, the correct formula is M - Z, which gives the number of neutrons.

  r₁ and r₂ are the radii of atomic nuclei of mass numbers 64 and 27 respectively. The ratio (r₁ /r₂) is

• 64/27             

• 27/64               

• 4/3                    

• 1

Answer explanation

The radius of a nucleus is proportional to the cube root of its mass number. Thus, r1/r2 = (A1/A2)^(1/3) = (64/27)^(1/3). This simplifies to 4/3, making the correct answer 4/3.

The mass defect of a nuclide can be calculated by

• A - (Z + N).

• (total mass of the electrons + nucleons) - mass of nuclide.

• mass of protons - mass of neutrons.

• N / Z

Answer explanation

The mass defect is calculated by subtracting the actual mass of the nuclide from the total mass of its constituent electrons and nucleons. This choice accurately reflects the definition of mass defect.

The force that keeps nucleons together is

• a strong nuclear force.

• a weak nuclear force.

• an electromagnetic force.

• a gravitational force.

Answer explanation

The strong nuclear force is the fundamental interaction that binds nucleons (protons and neutrons) together in the nucleus, overcoming the repulsive electromagnetic force between positively charged protons.