Basics of Undergraduate/university fellows It is not in range of human senses or un-aided detection for measurement.

1. ISOTOPES 1
ISOTOPES
 In ISOTOPES;
1. Atomic number (Z) = Number of Protons = Constant
2. Atomic mass number = Number of Protons + Neutrons = Shall vary
 Isotopes are the elements containing same atomic number (Protons), but a different
mass number (Protons + Neutrons=Nucleon number).
 81 stable elements have 275 different isotopes.
 Isotopes have similar chemical properties, but have different physical properties
(Expect: Hydrogen)
Atomic Mass←1H1→Atomic Number
IMPORTANCE IN BIOLOGICAL STUDIES
 Radio Isotopes facilitates new discoveries and disease profiling
 Radio-Tracing unblocks various sectors enabling elucidation of in-vivo processes.
 Non-Invasive mode of therapy using nuclear medical kit and radio pharmaceuticals.
 To elucidate the metabolic pathway, metabolic turn over time of a molecule.
 Radioactive hybridizationis also utilized vaccine production.
ELEMENTS ISOTOPES
Hydrogen 1H, 2H,3H
Carbon 12C, 13C, 14C
Oxygen 16O, 17O, 18O
Uranium 235U, 238U
Chlorine 35Cl, 37Cl
Fluorine 17F,18F, 19F
Classification of Isotopes based on Stability
1. STABLE ISOTOPE 2. RADIOACTIVE ISOTOPE
Example 12C 13C, 14C
Proton + Neutron Stable Unstable
Decay effect Absent Present - Radioactive Decay
Reason for the
stability
Number of Neutrons are
balanced
Neutrons disintegration is
documented
Radiation emission No 3 types of radiation are emitted
1. Alpha - α
2. Beta - β
3. Gamma - γ
Energy release No Yes
Impact on human
health
No much significant affect Increased health risk
Uses Identification of ancient
rock & minerals
Important tool in field of science
especially in medicine and
industrial applications
Classification of Isotopes based on their origin
1. Long lived
Isotopes
2. Cosmogenic
Isotopes
3. Anthropogenic
Isotopes
4. Radiogenic
Isotopes
Origin During solar
system genesis
During Star
formations
During human
led nuclear act
ivies
During
radioactive
decay
Approximate
duration
447 billion
years ago
10,000–30,000
years ago
50-100
years ago
_ _ _

2. ISOTOPES 2
 In clinicaldiagnosis to detect tumor, blood clots, infection.
 Neuro imaging, pharmacological studies, non-invasive therapies for hyper-thyrodism
and cancer (Radio-immunotherapy).
 Based on the radioactivity of the elements in the nature, evolutionarist speculate the
phyllogenetic tree.
 Radiation is used as a mutagen to produce mutants for scientific studies.
OTHER USES
 Sterilization and food irradiation in Industries.
 Geochemists use radio isotopes to analyze the composition of geological materials.
MEASURE OF RADIOACTIVITY
 It is not in range of human senses or un-aided detection for measurement.
Unit for measurement of Radioactivity
For Chemicals For Human For Risk Assessment
S.I unit Becquerel (Bq) Gray (Gy) Sievert (Sv)
Conventional unit Curie (Ci) Radiation absorbed
dose (rad)
Roentgen equivalent
man (rem)
Comparison Amount of Rain fall Amount of rain drops
on any object
Amount of rain drop
precipitating on object
Basic general principle for measurement of Radioactivity
Measurement of Radioactivity
1. Gas-filled Counters (example: Geiger Muller [GM] Counter)
2. Scintillation Counter
3. Semi-Conductor Detectors
1. Geiger Muller [GM] Counter
 Nuclear physicist Hans Geigeris the co-inventor of Geiger-Muller counter (GM tube), a
device used for the detection and measurement of all types of radiation: alpha, beta
and gamma radiation.
 GM tube is a gas filled device used to detect ionising radiation, monitor and counted
by electric circuit.
 Output is reported as counts per second or Rontgens per hour.
WORKING PRINCIPLE
GM tube filled with inert gas (Helium, Neon & Argon) at low pressure connected to
High voltage source conducts electrical charge on particles or photons, ionising the gas
conductives followed by amplification and according to discharge effect electrical
charge released are counted as pulse, displayed as digital output in the meanwhile
generates audio beeps in the speaker confirming the presence of radiation.

3. ISOTOPES 3
APPLICATIONS
1. To detect alpha, beta and gamma radiation from given sample.
2. To check for environmental levels of radioactivity.
3. In risk assessment in various working places.
4. To identify radioactivity in rocks and minerals.
ADVANTAGES
1. Relatively less expensive
2. Durable
3. Easily portable
4. Detect all types of ionising radiation
DISADVANTAGES
1. Fails to differentiate between  or β or γ radiation.
2. Cant estimate exact energy level.
3. Very low efficiency.
SCINTILLATION COUNTER
 It is one among the oldest and commoniest methods of particle detection.
 In 1945, photomultiplier tubes were invented to detect slightiest light particles.
 Scintillation counter is an instrument for detecting and measuring ionizing radiation
by using the excitation effect of incident radiation on a scintillator material, and
detecting the resultant light pulses.
 It consists of a scintillator which generates photons in response to incident radiation. a
sensitive photomultiplier tube (PMT) which converts the light to an electrical signal and
electronics to process this signal.

4. ISOTOPES 4
WORKING PRINCIPLE
When radiation is passed on fluroscent material (example: Zinc sulfide, thallium-activated
sodium iodide), Scintillations (flashes of light) are produced and are converted into electric
pulses by Photoelectric alloy (either of cesium and antimony), amplified about million
times by photomultiplier tube and counted in the counter.
Applications of Scintillation Counter
1. Scintillation Counters are widely used in radioactive contamination, radiation survey
meters, radiometric assay, nuclear plant safety and medical imaging, that are used to
measure radiation.
2. There are several counters of mounted on helicopters and some pickup trucks for
rapid response in case of a security situation due to radioactive waste or dirty bombs.
3. Scintillation counters designed for weighbridge applications, freight terminals, scrap
metal yards, border security, contamination monitoring of nuclear waste and ports.
4. It is widely used in Screening technologies, In vivo and ELISA alternative technologies,
cancer research, epigenetics and Cellular research.
5. It also has its applications in Protein interaction and detection, academic research
and Pharmaceutical.
6. Liquid Scintillation Counter is a type of scintillation counter that is used for measuring
the beta emission from the nuclides.