Nuceli Part-1
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CHAPTER 13 NUCLEI
- 13.1 Introduction
- 13.2 Atomic Masses and Composition of Nucleus
- 13.3 Size of the Nucleus
- 13.5 Nuclear Force
- 13.6 Radioactivity
- 13.7 Nuclear Energy
NCERT Solutions class 12 physics Nuclei Part 1
1: (a) Two stable isotopes of lithium 
and 
have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.
(b) Boron has two stable isotopes, 
and
. Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is 10.811 u. Find the abundances of and .
2: The three stable isotopes of neon: 
and 
have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u, respectively. Obtain the average atomic mass of neon.
3: Obtain the binding energy (in MeV) of a nitrogen nucleus
, given 
=14.00307 u
4: Obtain the binding energy of the nuclei 
and 
in units of MeV from the following data: 
= 55.934939 u 
= 208.980388 u
5: A given coin has a mass of 3.0 g. Calculate the nuclear energy that would be required to separate all the neutrons and protons from each other. For simplicity assume that the coin is entirely made of 
atoms (of mass 62.92960 u).
6: Write nuclear reaction equations for
(i) α-decay of 
(ii) α-decay of 
(iii) 
(iv) 
(v) 
(vi) 
(vii) Electron capture of 
7: A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to a) 3.125%, b) 1% of its original value?
8: The normal activity of living carbon-containing matter is found to be about 15 decays per minute for every gram of carbon. This activity arises from the small proportion of radioactive 
present with the stable carbon isotope
. When the organism is dead, its interaction with the atmosphere (which maintains the above equilibrium activity) ceases and its activity begins to drop. From the known half-life (5730 years) of, and the measured activity, the age of the specimen can be approximately estimated. This is the principle of dating used in archaeology. Suppose a specimen from Mohenjodaro gives an activity of 9 decays per minute per gram of carbon. Estimate the approximate age of the Indus-Valley civilisation.
9: Obtain the amount of 
necessary to provide a radioactive source of 8.0 mCi strength. The half-life of is 5.3 years.
10: The half-life of 
is 28 years. What is the disintegration rate of 15 mg of this isotope?
11: Obtain approximately the ratio of the nuclear radii of the gold isotope 
and the silver isotope
.
12: Find the Q-value and the kinetic energy of the emitted α-particle in the α-decay of (a) and (b)
. Given 
= 226.02540 u, 
= 222.01750 u,
= 220.01137 u, 
= 216.00189 u.
13: The radionuclide 11C decays according to 
The maximum energy of the emitted positron is 0.960 MeV.
Given the mass values:
and 
calculate Q and compare it with the maximum energy of the positron emitted
14: The nucleus 
decays by
emission. Write down the
decay equation and determine the maximum kinetic energy of the electrons emitted. Given that:
= 22.994466 u
= 22.989770 u.
15: The Q value of a nuclear reaction 
is defined by
Q = 
where the masses refer to the respective nuclei. Determine from the given data the Q-value of the following reactions and state whether the reactions are exothermic or endothermic.
(i) 
(ii) 
Atomic masses are given to be
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