The atomic nucleus is at the center of atoms and is composed of protons and neutrons. It was discovered in 1911 by Ernest Rutherford based on experiments showing that atoms have small, dense, positively charged nuclei. The nucleus contains nearly all of an atom's mass. Protons and neutrons are bound together in the nucleus by the strong nuclear force. Nuclear chemistry deals with the composition, properties, and reactions of atomic nuclei. Key discoveries included the neutron by Chadwick in 1932 and the development of nuclear models showing electrons orbiting the positively charged nucleus.

1. ATOMIC NUCLEUS
INTRODUCTION:
The atomic nucleus is the central part of the atom. The atomic nucleus is the small, dense region
consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest
Rutherford based on the 1909 Geiger–Marsden gold foil experiment.
After the discovery of the neutron in 1932, models for a nucleus composed of protons and
neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg.
An atom is composed of a positively-charged nucleus, with a cloud of negatively-
charged electrons surrounding it, bound together by electrostatic force.
Almost all of the mass of an atom is located in the nucleus, with a very small contribution from
the electron cloud. Protons and neutrons are bound together to form a nucleus by the nuclear
force.
NUCLEAR CHEMISTRY:
The branch of chemistry which deals with composition, properties, and reactions of atomic
nuclei is called as Nuclear Chemistry.
It is used in Atomic Bomb , Hydrogen Bomb ,Power Plants ,Nuclear Reactions ,Stability of Nucleus
,Radioactivity ,Effect of radiations on Biological System.
NUCLEAR REACTIONS CHEMICALREACTIONS
1. In these reactions elements (isotopes)
are converted into another elements.
1. In these reactions atoms are
rearranged and new compounds are
formed.
2. In nucleus of an atom. 2. In valence shell .
3. No breaking of bonds. 3. Breaking of bonds
4. Nuclear phenomena only. 4. Extra nuclear phenomenas
5. Exothermic always. 5. Exo or endo .
6. No effect of T and P. 6. Depends on upon T and P
7. Irreversible only. 7. Both reversible and irreversible
reaction occur (Law of conservation
of Mass)
8. Mass is not conserved and mass is
converted into energy.
8. Mass is conserved
9. Million time of energy involves. 9. Less energy is required
10. Obeys only 1st order kinetics. 10.Zero,1st,2nd.3rd,order kinetic follows

2. STRUCTURE OF ATOM:
According to John Dalton: Atom is derived from Greek word Atomos means indivisible
(unbreakable) particle .
According to J.J.Thomson : Electrons reside within a sphere of uniform positive charge (Plum
Pudding Model)
According to Rutherford : The existence of a positively charged nucleus that contains nearly all the mass
of an atom.
According to Bhor Model : Fixed circular orbits (quantized) around the nucleus for electrons in
an atom .
 Each shell energy is quantized (E=nh𝜈).
 Angular momentum of electrons should be equal to L = mvr = n(
ℎ
2𝜋
) .

3. According to Chadwick : He discovered nuetrons and said that inside an atom neucleus
,neutural species are also present equal to proton number .
According to Sommer field : Sommerfeld model of an atom is extended version of Bohr’s atomic
model, which was formed by Sommerfield to explain the fine spectral line phenomenon which Bohr
was not able to explain.
According to Sommerfeld, the stationary orbits in which electrons are revolving around the
nucleus in an atom are not circular but elliptical in shape.
It is due to the influence of the centrally located nucleus. The electron revolves in elliptical path
with nucleus at one of its foci. So there will be a major and a minor axis of the path.
ATOMIC NUCLEUS:
The nucleus is the central core of an atom. It consists of Neutrons and protons which are called as
Nucleons.

4. Other particles are produced (emitted) during nuclear reactions.
J.J.Thomson (discovery of cathode rays) and Rutherford experiment (discovery of nucleus) proved
structure of nucleus.
PROPERTIES OF NUCLEUS :
 According to atoms, electrons revolving in orbits .
 Similarly protons and neutrons are also revolving in their shells and sub-shells.
 Nuclear energy is much more than chemical energy .
 X-ray and 𝛾 rays are emitted due to these shells of Protons and Neutrons .
NUCLEAR SPIN :
Protons and Neutrons are spinning and leave orbital motion. Due to motion of protons and
neutrons an angular momentum is created. The nuclear spin is shown by ‘ I ’.
The nuclear spin for Odd mass no. are : 1
2⁄ , 3
2⁄ , 5
2⁄ ,………etc.
The nuclear spin for Even mass no. are: 1, 2, 3, 4, ………..etc.
NUCLEAR MAGNETIC MOMENT :
When a particle (electron or proton) rotate in a shell or sub-shell, then it behaves like a small
magnet and produces a Magnetic Dipole.
The magnetic properties of electrons are used in ESR and that of Nucleus is used in NMR
Spectrometers.
DISCOVERY OF PROTONS:
Protons are positively charged particles found within the nuclei.Between 1911 to 1919 Rutherford
conducted experiment in cathode ray tube.
Protons are slightly smaller than neutrons.
The number of protons defines what element it is. Carbon have six while oxygen have eight
protons.
ATOMIC NUMBER:
The number of protons inside a nucleus called atomic number or the charge number of an atom.
As Protons define the entire charge of a nucleus, and hence its chemical identity.
Three quarks made up each protons ( one down quark and two up quark ).
These quarks are held together by sub-atomic particles called Gluons which are massless .

5. DISCOVERY OF ELECTRONS:
Electrons are tiny as compared to protons and electrons. Over 1800 times smaller than either a
proton or a neutron.
When a discharge tube is filled with a gas and when high voltage is applied across electrodes than
rays are produced that creates flouresence over the glass wall opposite the cathode.
These are made up of three quarks ( one up quark and two down quarks ) .
DISCOVERY OF NEUTRONS:
Protons and neutrons were discovered in 1886 and their complete properties were determined in
1805. Rutherford predicted in 1920 that some kind of neutral particles present inside the nucleus
having mass equal to protons. Chadwick in 1932 discovered neutrons and was awarded Nobel
Prize in Physics in 1935.
ATOMIC MASS:
The combined number of all the protons and neutrons in a nucleus is known as its atomic mass
number OR also known as Nucleon number.
It is denoted by ‘ A ’.
The number of neutrons N present in a nucleus is given by
N = (A –Z )
NUCLIDES:
A nuclide is a distinct kind of atom or nucleus characterized by a specific number of protons and
neutrons.
The word nuclide was proposed by Trumann P.Kohman.
NUCLIDES VS ISOTOPES :
A nuclide of an atom is with specific number of protons and neutrons.
But isotopes have that have same number of protons but different number of neutrons .
ISOBARS :
It is a set of nuclide with equal mass number but different atomic number .
ISOTONES:
The nuclides with equal neutron number but proton number are known as isotones.

6. PARTICLES OF ATOM:
Particles may be stable ( protons ,electrons) and may be unstable ( neutrons ,positrons). Each
particle has charge ,mass ,spin.
PARTICLES SYMBOL CHARGE MASS
Electron 𝑒−
, 𝛽−1 -1 1
Proton P +1 1836.1
Neutron N 0 1836.1
Positron e+, 𝛽+ +1 1
Neutrino 𝜈 0 0
Anti-neutrino 𝜈̃ 0 0
Meson 𝜇 ± 0.1152
Photon 𝛾 0 0
Graviton G 0 0
Anti-proton 𝑝̅ _ 1.00758
V-particle V ± 1.2014
COMPOSED BY
MARIA AAMER SABAH
ROLL NO. MCEC-17-09
BS CHEMISTRY 6th
semester