In 1909, Rutherford performed the Gold Foil Experiment and suggested the following characteristics of the atom: It consists of a small core, or nucleus, that contains most of the mass of the atom This nucleus is made up of particles called protons, which have a positive charge The protons are surrounded by negatively charged electrons, but most of the atom is actually empty space. In 1913, Bohor proposed the Atomic Model, which suggests that electrons travel around the nucleus of an atom in orbits or definite paths. Atom consists of a tiny nucleus. Each orbit has fixed energy that is quantatized. The energy is emitted or absorb only when an electron jumps from one orbit to another. Electron can revolve in orbits of fixed angular momentum mvr. Liquid Drop Model The nuclei of all elements are considered to be behave like a liquid drop of incompressible liquid of very high density. In an equilibrium state the nuclei of atoms remain spherically symmetric under the action of strong attractive nuclear forces just like the drop of a liquid which is spherical due to surface tension. The density of a nucleus is independent of its size just like the density of liquid which is also independent of its size. The protons and neutrons of the nucleus move about within a spherical enclosure called the nuclear potential barrier just like the movement of the molecules of a liquid within a spherical drop of liquid. . The binding energy per nucleon of a nucleus is constant Binding Energy The binding energy, BE, of a nucleus is a measure of the strong force and represents the energy required to separate the nucleus into its constituents protons and neutrons; Greater the binding energy, the more stable the nucleus. Volume The volume of the nucleus is directly proportional to the total number of nucleons present in it. Density The density of the nucleus is nearly constant.

1. Presented by : Muhammad Awais
Roll Number : MME-15-02
Subject : Nuclear Engineering
Institute of Advanced Materials Bahauddin
Zakaria University Multan
Nuclear Structure

2. Table of Contents
 Ruthorford Atomic model
 Bohrs Atomic model
 Liquid drop model
 Shell Model
 Four Fundamental forces
 Quark Model of nucleons
 Strong Nuclear Force
 Weak Nuclear Force

3. Rutherford Atomic Model
 In 1909, Rutherford performed
the Gold Foil Experiment and
suggested the following
characteristics of the atom:
 It consists of a small core, or
nucleus, that contains most of
the mass of the atom
 This nucleus is made up of
particles called protons, which
have a positive charge
 The protons are surrounded by
negatively charged electrons,
but most of the atom is actually
empty space

4. Neil Bohor’s Atomic Model
 In 1913, Bohor proposed the
Atomic Model, which suggests that
electrons travel around the nucleus of
an atom in orbits or definite paths.
 Atom consists of a tiny nucleus.
 Each orbit has fixed energy that is
quantatized.
 The energy is emitted or absorb only
when an electron jumps from one
orbit to another.
 Electron can revolve in orbits of fixed
angular momentum mvr.

5. Liquid Drop Model
This model is also introduced by Neils Bohor`
Assumptions
1. The nuclei of all elements are considered to be behave like a liquid drop
of incompressible liquid of very high density.
2. In an equilibrium state the nuclei of atoms remain spherically symmetric
under the action of strong attractive nuclear forces just like the drop of a
liquid which is spherical due to surface tension.
3. The density of a nucleus is independent of its
size just like the density of liquid which is also
independent of its size.
1. The protons and neutrons of the nucleus move about
within a spherical enclosure called the nuclear
potential barrier just like the movement of the
molecules of a liquid within a spherical drop of liquid.

6. Liquid Drop Model
5. The binding energy per nucleon of a
nucleus is constant
 Binding Energy
 The binding energy, BE, of a nucleus is a
measure of the strong force and
represents the energy required to separate
the nucleus into its constituents protons
and neutrons;
 Greater the binding energy, the more
stable the nucleus.
 Volume
 The volume of the nucleus is directly
proportional to the total number of
nucleons present in it.
 Density
 The density of the nucleus is nearly
constant.

7. Shell Model
 The nuclear shell model is a model of the atomic nucleus
which uses the Pauli exclusion principle to describe the
structure of the nucleus in terms of energy levels.
 The first shell model was proposed in 1932.
 In this model it is assumed that the protons and neutrons
move in its orbit within the nucleus , independently of all
other nucleons.
 Each nucleon is identified by its own set of quantum
numbers similar to the electrons in their orbits.

8. Shell Model
 If we have nucleons which has certain number of neutrons and
protons and whenever these numbers correspond to certain
numbers which are known as magic numbers then u end up
getting extremely stable nuclear configuration.
 These magic numbers are 2, 8, 20, 28, 50, 82 and 126.
 For example : Ni-58 has 28 protons and 30 neutrons and 28 is a
magic number so its stable nuclei.
 If both the number of protons and neutrons correspond to magic
numbers then it considered as double magic numbers.
 For example:
 Helium has 2 neutrons and 2 protons so it is a double magic
number

9.  For every value of n there will
be different value of l such
that
l <= n
 Even n will correspond
to even l
 Odd value will correspond to
odd value of l
 Due to spin orbit interaction
each energy level would split
into two energy levels such
that
j = l – 1/2
j = l + 1/2
 When value of n is more than
2 then for a given value of n
splitting of energy level would
increase by increasing value
of l such that value of
j = l + 1/2
Will slide down and get
associate with the value of n-
1

10. Shell Model
 Rules
 For every value of n there will be different
value of l such that
l <= n
 Even n will correspond to even l
 Odd value will correspond to odd value of l
 Due to spin orbit interaction each energy
level would split into two energy levels such
that
j = l – 1/2
j = l + 1/2
 When value of n is more than 2 then for a
given value of n splitting of energy level
would increase by increasing value of l such
that value of
j = l + 1/2
Will slide down and get associate with the
value of n-1
Note
 j = orbital angular
momentum + spin orbital
momentum
 j = l + s
 j = l - s
 Spin for proton and
neutron is
s = 1/2

11. Note
j = orbital angular momentum + spin orbital momentum
j = l + s
j = l - s
Spin for proton and neutron is
s = 1/2
Azimuthal
Quantum
Number (l)
Orbitals Max. No. of
nucleons
2*(2*l + 1)
Total Angular
Momentum
( j = l - s )
( j = l + s )
2j + 1
0 s 2 1/2 2
1 p 6 1/2, 3/2 2,4
2 d 10 3/2,5/2 4,6
3 f 14 5/2,7/2 6,8
4 g 18 7/2,9/2 8,10
5 h 22 9/2,11/2 10,12
6 i 26 11/2,13/2 12,14

12. Fundamental Forces
 The Four Fundamental
Forces of Nature are
1. Gravitational force
2. Weak Nuclear force
3. Electromagnetic force
4. Strong Nuclear force.

13. Quark Structure of Nucleons

14. Strong Force
 It is responsible for holding the
nuclei of atoms together.
 This force is 100 times stronger
than repulsive columbic forces
between protons.
 The strong force is ‘carried’ by
particles called gluons; that is,
when two particles interact
through the strong force, they
do so by exchanging gluons.
 Thus, the quarks inside of the
protons and neutrons are bound
together by the exchange of the
strong nuclear force.

15. Weak Nuclear Force
 Weak force/interaction is associated
with elementary particles bosons
which act as force carriers between
quarks and/or laptops.
 Weak force is the weaker than
electromagnetic force and strong
nuclear force but it is stronger than
gravitational force.
 W and Z bosons are the force
carriers of weak interaction.
 weak force is responsible for the
decay of neutron which is known as
beta-decay.
 Mechanism of beta decay
 Down quark emits a W- boson
which then decay into particles
electron and anti-electron
neutrino particle.