Unit 1 Nuclear Chemistry
Nuclear structure, mass and charge, mass defect, binding energy, stability rules, magic num
nuclear quantum numbers, nuclear parity and statistics, models of nucleus, shell model, li
drop model, , semi empirical mass equation, equations of radioactive decay and growth, ha
average life determination of half-lives, nuclear reactions, energetics of nuclear reactions,
of nuclear reactions, spontaneous and induced fission, neutron capture cross sections- cri
size principle and working of nuclear reactor. Numerical problems relevant to each sessi
,J. J. Thomson in
Ernest Rutherford in James Chadwick in Carl Anderson in Emilio
1897-electron
1920-Proton 1932-neutron 1932-Positron 1955-A
Neutrino-Fredrick Reiner, leon M Lenderson, Jack Steinberger 1930
Antineutrino-Fred Reiner 1956
Meson-Yukawa Hideki 1947
Leptons-Carl D Handerson 1897
Hadrons-Carl D Handerson 1968
Bosons-Sathyendra Nath Boson 1961
Fermions-Tony Skyrme 1960
Bruce Cork in Quarks-Murray Gell-Mann and George Zweig 1964
1956-Antineutron Baryon-Eugene Wigner 1937
,Nucleus contains 99.95% of the total mass of the atom and a posi
charge equivalent to the number of electrons surrounding it.
While discussing about the nuclear structure, the following three m
concepts have to be discussed in detail
1. Composition of the nucleus
2. Nuclear forces
3. Models of the nucleus
,1. Electron-proton concept: Before the discovery of
neutron in 1932, it was believed that nucleus consist
of protons and electrons.
• Merits- This could explain the emission of α and β
particles
• Demerits-Size of electron is approximately same as
that of nucleus
Could not explain angular momentum of
nuclei
Could not explain dual β decal (e- and e+)
2. Proton-neutron concept: It introduces the presence
of neutral particles in nucleus and protons give
enough positive charge. The number of protons and
neutrons are almost equal in lighter elements, but
as atomic weight increases, number of neutrons
becomes high.
3. Neutron-positron concept
4. Antiproton-neutron concept
The proton-neutron model is the still accepted one.
,• Nuclear forces (also known as nuclear interactions or strong forc
are the forces that act between two or more nucleons. They b
protons and neutrons (“nucleons”) into atomic nuclei. The nuc
force is about 10 millions times stronger than the chemical bind
that holds atoms together in molecules.
• This is the reason why nuclear reactors produce about a million tim
more energy per kilogram fuel as compared to chemical fuel like o
coal.
• However, the range of the nuclear force is short, only a
femtometer (1 fm =10−15 m), beyond which it decreases rapidly. T
is why, in spite of its enormous strength, we do not feel anything
this force on the atomic scale or in everyday life.
,1. Saturation property: Each nucleon interact with only a
limited number of nucleons nearest to it.
2. Charge independence: Nuclear forces between 2
protons or between 2 neutrons or between a proton
and a neutron are same. So nuclear forces are
independent of charge.
3. Nuclear forces are short range forces: Nuclear forces
occur only when the distance between the nucleons
is of the order of 10-15 m or less. This distance is
action radii or range of nuclear forces.
4. Nuclear forces are not central forces: This suggests a
force that depends on the orientation of the spins of
the nucleons with regard to the vector joining the two
nucleons (a tensor force).
, Question Pool
1. List out the elementary particles present in an atom with a b
explanation about each.
2. Detail the different concepts of composition of nucleus.
3. What are nuclear forces? What is its significance?
4. Explain the four different properties of nuclear forces.
,1. Exchange theory (Heisenberg and Majorana)
‘When a neutron interacts with a proton, a single electric charge jumps f
one nucleon to other so that in the jump the original proton changes t
neutron and the neutron into a proton’
This was done in analogy to the quantum mechanical theory
covalent bonds, such as exist between two hydrogen atoms in
hydrogen molecule wherein the chemical force is attractive if the w
function is symmetric under exchange of coordinates of the electr
and is repulsive if the wave function is anti-symmetric in this respect
This theory could well explain the continuous beta decay and rela
phenomena, but the magnitude of nuclear forces obtained fr
theoretical and experimental studies were not matching.
,2. Yukawa theory
He predicted the existence of a new particle and modified exchange th
proposed that exchange particles are not electron or neutrino but the new
meson which has the rest mass between electron and proton.
When a proton and neutron interact, p may emit a +ve meson which is absor
So in the exchange of +ve meson, p→n. Similarly a n may interact a p by em
meson and in this process n→p.
𝑝 = 𝜋 + + 𝑛 𝑎𝑛𝑑 𝑛 = 𝜋 − + 𝑝
Demerit: It does not account for the forces between like particles like p-p
interactions
, 3. Modification of Yukawa theory:
To account for binding forces between like particles, N
Kemmer reasoned that there must be a neutral meson.
The interaction between like particles may be represented
as
𝑝 = 𝜋 0 + 𝑝 𝑎𝑛𝑑 𝑛 = 𝜋 0 + 𝑛
4. Nuclear fluid theory:
According to this theory nucleons are present in the
nucleus in the form of a nuclear fluid which has very high
density (130 million tons/ml). Due to this high density
surface tension of nuclear fluid is very high in space and
distance between particles in the nucleus is very small and
due to high surface tension, nucleons are bound together
despite the presence of repulsive forces.
Nuclear structure, mass and charge, mass defect, binding energy, stability rules, magic num
nuclear quantum numbers, nuclear parity and statistics, models of nucleus, shell model, li
drop model, , semi empirical mass equation, equations of radioactive decay and growth, ha
average life determination of half-lives, nuclear reactions, energetics of nuclear reactions,
of nuclear reactions, spontaneous and induced fission, neutron capture cross sections- cri
size principle and working of nuclear reactor. Numerical problems relevant to each sessi
,J. J. Thomson in
Ernest Rutherford in James Chadwick in Carl Anderson in Emilio
1897-electron
1920-Proton 1932-neutron 1932-Positron 1955-A
Neutrino-Fredrick Reiner, leon M Lenderson, Jack Steinberger 1930
Antineutrino-Fred Reiner 1956
Meson-Yukawa Hideki 1947
Leptons-Carl D Handerson 1897
Hadrons-Carl D Handerson 1968
Bosons-Sathyendra Nath Boson 1961
Fermions-Tony Skyrme 1960
Bruce Cork in Quarks-Murray Gell-Mann and George Zweig 1964
1956-Antineutron Baryon-Eugene Wigner 1937
,Nucleus contains 99.95% of the total mass of the atom and a posi
charge equivalent to the number of electrons surrounding it.
While discussing about the nuclear structure, the following three m
concepts have to be discussed in detail
1. Composition of the nucleus
2. Nuclear forces
3. Models of the nucleus
,1. Electron-proton concept: Before the discovery of
neutron in 1932, it was believed that nucleus consist
of protons and electrons.
• Merits- This could explain the emission of α and β
particles
• Demerits-Size of electron is approximately same as
that of nucleus
Could not explain angular momentum of
nuclei
Could not explain dual β decal (e- and e+)
2. Proton-neutron concept: It introduces the presence
of neutral particles in nucleus and protons give
enough positive charge. The number of protons and
neutrons are almost equal in lighter elements, but
as atomic weight increases, number of neutrons
becomes high.
3. Neutron-positron concept
4. Antiproton-neutron concept
The proton-neutron model is the still accepted one.
,• Nuclear forces (also known as nuclear interactions or strong forc
are the forces that act between two or more nucleons. They b
protons and neutrons (“nucleons”) into atomic nuclei. The nuc
force is about 10 millions times stronger than the chemical bind
that holds atoms together in molecules.
• This is the reason why nuclear reactors produce about a million tim
more energy per kilogram fuel as compared to chemical fuel like o
coal.
• However, the range of the nuclear force is short, only a
femtometer (1 fm =10−15 m), beyond which it decreases rapidly. T
is why, in spite of its enormous strength, we do not feel anything
this force on the atomic scale or in everyday life.
,1. Saturation property: Each nucleon interact with only a
limited number of nucleons nearest to it.
2. Charge independence: Nuclear forces between 2
protons or between 2 neutrons or between a proton
and a neutron are same. So nuclear forces are
independent of charge.
3. Nuclear forces are short range forces: Nuclear forces
occur only when the distance between the nucleons
is of the order of 10-15 m or less. This distance is
action radii or range of nuclear forces.
4. Nuclear forces are not central forces: This suggests a
force that depends on the orientation of the spins of
the nucleons with regard to the vector joining the two
nucleons (a tensor force).
, Question Pool
1. List out the elementary particles present in an atom with a b
explanation about each.
2. Detail the different concepts of composition of nucleus.
3. What are nuclear forces? What is its significance?
4. Explain the four different properties of nuclear forces.
,1. Exchange theory (Heisenberg and Majorana)
‘When a neutron interacts with a proton, a single electric charge jumps f
one nucleon to other so that in the jump the original proton changes t
neutron and the neutron into a proton’
This was done in analogy to the quantum mechanical theory
covalent bonds, such as exist between two hydrogen atoms in
hydrogen molecule wherein the chemical force is attractive if the w
function is symmetric under exchange of coordinates of the electr
and is repulsive if the wave function is anti-symmetric in this respect
This theory could well explain the continuous beta decay and rela
phenomena, but the magnitude of nuclear forces obtained fr
theoretical and experimental studies were not matching.
,2. Yukawa theory
He predicted the existence of a new particle and modified exchange th
proposed that exchange particles are not electron or neutrino but the new
meson which has the rest mass between electron and proton.
When a proton and neutron interact, p may emit a +ve meson which is absor
So in the exchange of +ve meson, p→n. Similarly a n may interact a p by em
meson and in this process n→p.
𝑝 = 𝜋 + + 𝑛 𝑎𝑛𝑑 𝑛 = 𝜋 − + 𝑝
Demerit: It does not account for the forces between like particles like p-p
interactions
, 3. Modification of Yukawa theory:
To account for binding forces between like particles, N
Kemmer reasoned that there must be a neutral meson.
The interaction between like particles may be represented
as
𝑝 = 𝜋 0 + 𝑝 𝑎𝑛𝑑 𝑛 = 𝜋 0 + 𝑛
4. Nuclear fluid theory:
According to this theory nucleons are present in the
nucleus in the form of a nuclear fluid which has very high
density (130 million tons/ml). Due to this high density
surface tension of nuclear fluid is very high in space and
distance between particles in the nucleus is very small and
due to high surface tension, nucleons are bound together
despite the presence of repulsive forces.
