Study Notes On Radioactivity - Download PDF!

By Astha Singh|Updated : May 2nd, 2023

Are you an Aspirant of CSIR-NET and looking for some short and reliable notes for Chemical Sciences to strong your base for preparations? We have got you covered!

Candidates preparing for their CSIR NET exam can really make their preparation journey easier with the help of some reliable study notes that cover the topics in the most simple way. We at BYJU'S Exam Prep have come up with the idea of providing short notes On Radioactivity which comes under the Physical Chemistry section of the Chemical Science syllabus. 

The short notes on Radioactivity are developed by our experienced subject-matter experts to provide you with the most standard and authentic set of study materials to be focused upon. The students need the best resources for their preparation to clear the CSIR NET examination, Here are the most reliable study notes to make the topics easier for you and also help you to save your time for the preparations for the upcoming CSIR-NET 2023 exam.

Short Note On The Radioactivity

Kinetics of nuclear disintegration:

  • Radioactive decay is a first-order process. Hence,



     N = number of radioactive nuclei at any time t;

    N0 = number of radioactive nuclei at t = 0;

  • Activity: Activity (A) = – dN/dt = λN


It is the phenomenon of spontaneous emission of particles, electromagnetic radiation, or both by unstable nuclei.



S.I. units:

Disintegration per second (symbol s–1 or DPS).

1 dps = 1 Bq (Becquerel)

Other units are as follows:

1 Ci (Curie) = 3.7 × 1010 dps.

1 Rd (Rutherford) = 106 dps

Specific activity = dps/gm

Half-life (t1/2): The time taken by half the nuclei (originally present) to decay:


Uses of Radioisotopes:

(i). Oxygen-18:  It is used to study reaction mechanisms. In photosynthesis, the O18 isotope is used in


(ii). Cobalt-60:  It is used to sterilize surgical instruments and to improve the safety and reliability of industrial fuel oil burners. Along with this, it is used in cancer treatment, food irradiation, gauges, and radiography.

(iii). Iodine-131:  It is used to treat thyroid disorders, (Graves's disease).

(iv). Cadmium-109: It is used to analyze metal alloys for checking stock, and scrap sorting.

(v). Calcium-47:  It is an important aid for biomedical researchers to study the cellular functions and bone formation in mammals.

(vi). Carbon-14:  It is a major research tool which helps in research to ensure that potential new drugs are metabolized without forming harmful by-products. It is used in biological research, agriculture, pollution control and archaeology.

(vii). Cesium-137: It is used to treat cancerous tumours to measure correct patient doses of radioactive pharmaceuticals to measure and control the liquid flow in oil pipelines to tell researchers whether oil wells are plugged by sand and to ensure the right fill level for packages of food, drugs and other products. (The products in these packages do not become radioactive).

(viii). Chromium-51: It is used in research in red blood cell survival studies.

(ix). Copper-67: When injected with monoclonal antibodies into a cancer patient, it helps the antibodies bind to and destroy the tumour.

(x). lodine-123:  It is widely used to diagnose thyroid disorders and other metabolic disorders including brain function.

Application of radioisotopes:

(i). Determination of the age of the rock-by-rock dating method: Let us consider a rock containing U-238 isotope formed many years ago. The age of this rock can be determined by considering its radioactive disintegration which is governed by the relation:


(ii). Determination of the age of recent objects by radio-carbon dating method:


Expected emission from unstable nucleus:

  1. n/p ratio above stability belt: Those nuclei which have a high value of n/p ratio (lie above the

stability belt) undergoes decay.


Beta-decay is possible whenever the mass of the original neutral atom is greater than the final atom.

  1. n/p ratio below stability belt:


It is observed in nuclei with A > 210.

Mass number & the atomic number of the daughter nucleus decrease by 4 & 2 respectively compared to the parent nucleus.

Alpha decay may take place spontaneously or it can be initiated.

Alpha decay is possible whenever the mass of the original neutral atom is greater than the sum of the masses of the final neutral atom and the neutral helium-4 atom.

All the alpha particles coming from a particular decay reaction have the same kinetic energy.



The q value is negative i.e., isolated protons will not decay into neutrons.

Positron decay is possible whenever the mass of the original neutral atom is greater than at least two

electron masses larger than the final atom.

K electron capture:


Electron capture takes place whenever the mass of the original neutral atom is larger than that of the final atom. Those nuclei having low n/p ratio can capture K shell electrons. X-rays are emitted during the process.


A lifetime of the metastable nucleus thus forms is less than 10–9 sec.

No. of neutron and proton remains unchanged while the quantum state of nucleon changes.

Some differences between nuclear and chemical reactions:


Chemical reaction

Nuclear reaction


No new element is formed.

A new element is formed.


Valence electrons of atoms generally participate in the reaction.

Only the nucleus of atoms participates in the reaction.


Balanced by the conservation of atoms.

Balanced by the conservation of nuclear charge and mass number (total number of neutrons and protons).


Mass conservation is obeyed.

Disobeys mass conservation.


Maybe exothermic or endothermic, liberating or absorbing relatively small amounts of energy.

Maybe exothermic or endothermic, liberating or absorbing relatively very high amounts of energy.


May be reversible.

Only Irreversible.


May obey the kinetics of any order.

Obeys only first-order kinetics.


The rate depends on external factors like temperature and catalytic conditions.

Rate is independent of any external condition.

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