Download on Nuclear Physics - Good Earth School

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
STRUCTURE OF THE ATOM AND NUCLEUS
o ATOM CONSISTS OF THE NUCLEUS AT ITS CENTRE WITH ELECTRONS REVOLVING
IN SPECIFIC SHELLS
o THE NUCLEUS CONSISTS OF PROTONS AND NEUTRONS
o 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.
o 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
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
THE ATOMS OF THE SAME ELEMENT HAVING THE SAME MASS NUMBER BUT
DIFFERENT ATOMIC NUMBER ARE CALLED ISOBARS
(e.g) 12Cl24 and 11Na24
THE ATOMS HAVING DIFFERENT NUMBER OF PROTONS BUT SAME NUMBER
OF NEUTRONS ARE CALLED ISOTONES.
(e.g) 11Na23 and 12Mg24
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
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
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
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.