1. NUCLEAR PHYSICS

2. THIS LESSON DEALS WITH
STRUCTURE OF THE NUCLEUS
ISOTOPES, ISOBARS, ISOTONES
RADIO ACTIVITY
PROPERTIES OF α PARTICLES
PROPERTIES OF β PARTICLES
PROPERTIES OF γ PARTICLES
CHANGES WITHIN THE NUCLEUS DUE TO
α, β , γ EMISSION
SOURCES OF RADIATION
HARMFUL EFFECTS OF RADIATION
SAFETY PRECAUTIONS
BACKGROUND RADIATIONS

3. STRUCTURE OF THE ATOM AND NUCLEUS
ATOM CONSISTS OF THE NUCLEUS AT ITS CENTRE WITH ELECTRONS REVOLVING IN SPECIFIC SHELLS
THE NUCLEUS CONSISTS OF PROTONS AND NEUTRONS
THE TOTAL NUMBER OF PROTONS DETERMINES THE ATOM’S PLACE IN THE PERIODIC TABLE AND IS CALLED THE ATOMIC NUMBER OF THE ELEMENT. THIS IS DENOTED BY THE SYMBOL Z. IT CONTROLS THE PHYSICAL AND CHEMICAL PROPERTIES OF AN ELEMENT.
THE PROTONS AND NEUTRONS TOGETHER ARE CALLED NUCLEONS WHICH IS CALLED THE MASS NUMBER OF THE ELEMENT. THIS IS DENOTED BY THE SYMBOL A.
THE ATOM IS SPECIFIED BY THE SYMBOL ZXA
(e.g) atomic number (Z) = 11
mass number ( A) = 23
Which means Z = 11 protons
A = 23 = number of protons + number of neutrons
therefore number of neutrons = 23 – 11 = 12

4. ISOTOPES ISOBARS ISOTONES
THE ATOMS OF THE SAME ELEMENT HAVING THE SAME ATOMIC NUMBER BUT DIFFERENT MASS NUMBER ARE CALLED ISOTOPES
(e.g) chlorine has two isotopes 17Cl35 and 17Cl37
ISOBARS
THE ATOMS OF THE SAME ELEMENT HAVING THE SAME MASS NUMBER BUT DIFFERENT ATOMIC NUMBER ARE CALLED ISOBARS
(e.g) 12Cl24 and 11Na24
ISOTONES
THE ATOMS HAVING DIFFERENT NUMBER OF PROTONS BUT SAME NUMBER OF NEUTRONS ARE CALLED ISOTONES.
(e.g) 11Na23 and 12Mg24

5. RADIO ACTIVITY What is radioactivity?
Radioactive decay (also known as nuclear decay or radioactivity) is the process by which the nucleus of an unstable atom loses energy by emitting radiations .
What makes some atoms radioactive?
Atoms found in nature are either stable or unstable. An atom is stable if the forces among the particles that make up the nucleus are balanced. An atom is unstable (radioactive) if these forces are unbalanced.
An element becomes radio active when
its atomic number becomes 82
there is an imbalance of protons and neutrons

6. RUTHERFORD’S EXPERIMENTAL STUDY ON THE NATURE OF BECQUEREL RAYS
RUTHERFORD studied experimentally that the radiations given out by a radioactive substance in the presence of either a magnetic or an electric field gets separated into three constituents.
Those which turn towards the negative plate are positively charged alpha α particles
Those which turn towards the positive plate are negatively charged beta β particles
Those which pass undeviated are the uncharged gamma γ particles

7. PROPERTIES OF ALPHA PARTICLES
positively charged. So they are deflected by electric or magnetic fields
ionizing power of alpha particles is maximum when compared to beta or gamma particles
penetrating power is the lowest when compared to beta or gamma particles
PROPERTIES OF BETA PARTICLES
negatively charged. So they are deflected by electric or magnetic fields
ionizing power of beta particles is less than alpha but more than gamma particles
penetrating power is more than alpha but less than gamma particles
PROPERTIES OF GAMMA PARTICLES
no charge. They are neither deflected by electric or magnetic fields
ionizing power of gamma particles are the lowest
penetrating power is the maximum when compared to alpha and beta particles

8. CHANGES WITHIN THE NUCLEUS IN ALPHA, BETA AND GAMMA EMISSION
If the nucleus of a radioactive element X of mass number A and atomic number Z emits an alpha particle, a new element Y is formed which has mass number equal to (A - 4) and atomic number (Z – 2)
If the nucleus of a radioactive element X of mass number A and atomic number Z emits an beta particle, a new element Y is formed which has the same mass number but the atomic number is increased by one
If the nucleus of a radioactive element X of mass number A and atomic number Z emits an gamma particle, there is no change in the mass number A and atomic number Z.

9. Have confidence. You will do well