The isotope O 16 8 has 8 protons, 8 neutrons and 8 electrons; while the isotope B 4 e 8 has 4 protons, 4 neutrons and 4 electrons. Yet the ratio of their atomic masses is not exactly 2 . Why?

The atomic mass is not only depends upon the number of nucleons but also on the binding energy of the nucleus. This energy is dependent on the size of nucleus also, Hence the atomic mass of an atom with 8 nucleons is not exactly twice of one with 4 nucleons.

The binding energy of B 4 e 9 nucleus is 58 . 0 M e V while that of H 2 e 4 nucleus is 28 . 3 M e V . But B 4 e 9 is less stable than H 2 e 4 . Why?

The stability of nuclei is the factor of the binding energy per nucleon and not only the binding energy. From the given data, it is indicated that, The binding energy of Be 4 9 = 58 . 0 MeV and number of nucleons = 9 , so the binding energy per nucleon is 58 9 = 6 . 33 MeV . Similarity, the binding energy per nucleon for He 2 4 = 28 . 3 4 = 7 . 1 MeV As the helium has more binding energy per nucleon, it is more stable.

E M B I B E

ISC Physics Class 12, Part-2>Chapter 16 - Mass-Energy Equivalence : Nuclear Binding Energy>QUESTIONS>Q 11

HARD

12th ICSE

IMPORTANT

Earn 100

By annihilation of one $γ$ -photon, an electron and a positron are obtained. If kinetic energy of the pair so obtained is $0.88 M e V$ , what was the energy of the photon?

Important Questions on Mass-Energy Equivalence : Nuclear Binding Energy

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 16 - Mass-Energy Equivalence : Nuclear Binding Energy>QUESTIONS>Q 12

The isotope

{}_{8}O^{16}

has

8

protons,

8

neutrons and

8

electrons; while the isotope

{}_{4}B e^{8}

has

4

protons,

4

neutrons and

4

electrons. Yet the ratio of their atomic masses is not exactly

2

. Why?

HARD

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 16 - Mass-Energy Equivalence : Nuclear Binding Energy>QUESTIONS>Q 13

What is the significance of binding energy per nucleon of a nucleus of a radioactive element?

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 16 - Mass-Energy Equivalence : Nuclear Binding Energy>QUESTIONS>Q 14

If the speed of light were half of its present value, what effect would it have on the binding energy of a nucleus?

MEDIUM

12th ICSE

IMPORTANT

ISC Physics Class 12, Part-2>Chapter 16 - Mass-Energy Equivalence : Nuclear Binding Energy>QUESTIONS>Q 15

The binding energies of helium and heavy-hydrogen nuclei are roughly $7 M e V / nucleon$ and $1 M e V / nucleon$ , nucleon respectively. Which nucleus is more stable?