Lesson Notes By Weeks and Term - Junior Secondary School 3






  • Basis Science Made Easy for JSS Three by F.I Kehinde et al
  • Basis Science Made Easy for JSS Two by F.I Kehinde et al
  • STAN Integrated Science for JSS Three
  • Precious Seeds Basic Science for JSSThree by J.O Otugboyega et al.






  • Meaning of Radioactivity
  • Discovery of Radioactivity
  • Types of Radioactivity
  • Radioactive Elements
  • Types of Radiation and Their Properties
  • Nuclear Transmutation
  • Uses of Radioactivity



Meaning of Radioactivity

Radioactivity is the spontaneous disintegration or breaking down of the nucleus of an atom which makes it give out or emit radiation. Any element that disintegrates spontaneously and release rays us called a radioactive element


Discovery of Radioactivity

Radioactivity was discovered by a French physicist called Henri Becquerel in 1896. He discovered that atoms of some elements gave out some kinds of ray which penetrated a thick black paper. He used uranium for his study. His discovery was confirmed by the couple, Merie and Pierre Curie.


Types of Radioactivity

There are two types of radioactivity.  i. Natural radioactivity   ii. Artificial radioactivity.

Natural radioactivity occurs on its own without man's influence.

Artificial radioactivity is caused by man's activity.


Radioactive Elements

Radioactive elements are elements that give out rays from the nuclei of their atoms. Natural radioactive elements include uranium, radium, plutonium, radon, thorium etc. Artificial radioactive elements are produced by bombarding nonradioactive elements (like sulphur-35, iodine-137, cobalt-60 etc.) with radioactive particles to form radioactive isotopes.



  1. What is radioactivity?
  2. What are the types of radioactivity?
  3. What are radioactive elements?


Types of Radiation and Their Properties

There are three types of rays, they are;  i. Alpha particles   ii. Beta particles  iii. Gamma rays


Alpha particles (α-rays)

Alpha particles or rays are helium nucleus consisting of two protons and two neutrons (I.e. atomic number and atomic mass are 2 and 4 respectively).

  1. Alpha particles are positively charged.
  2. They have the heaviest radiation.
  3. They have the lowest penetrating power and can be stopped by a thin sheet of paper.
  4. They have the highest ionization power.


Beta particles (β-rays)

Beta particles or rays consist of a stream of fast moving electrons.

  1. They are heavier than gamma rays.
  2. They are negatively charged.
  3. They have higher penetrating power than alpha rays. They can be stopped by aluminum foil.


Gamma rays (ϒ-rays)

Gamma rays are electromagnetic radiation.

  1. They do not carry any charge.
  2. They have negligible mass.
  3. They have the highest penetrating power and can only be stopped by lead block.
  4. They have the lowest ionization power.


Nuclear Transmutation

The changes in the nucleus of the atom of an element caused by radioactive emission are called nuclear transmutation. For instance, Radium-226 emits -rays and turns to radon-222. 

22688Ra--->42He + 22286Rn

If the changes in the nucleus are caused by man, it is called artificial nuclear transmutation.



  1. Differentiate between alpha, beta and gamma radiations.
  2. What is nuclear transmutation?


Uses of Radioactivity

Radioactivity has application in the following fields;

  1. The medical field.
  2. Agricultural and scientific research.
  3. The industrial field.


In medical field

Radioactivity is used in;

  • Sterilization of syringes and medical equipment.
  • Treatment of cancer.
  • Sterilization of bottled drinks and canned food.


In agricultural and scientific research

Radioactivity is used as;

              1. Radioactive tracers.
  1. Radioactive or carbon dating.


In industrial field

Radioactivity is used to;

  • Study defects in metals and welded joints.
  • Check metal weaknesses.
  • Trace underground pipe leakages.


Effect or dangers of using radiation

  1. Long exposure to radiation can destroy body cells.
  2. Exposure to radiation can lead to gene mutation.
  3. It can cause deformities to foetus in the womb.
  4. Radiation from nuclear weapons can kill.
  5. Radioactive wastes pollute and destroy the environment.



  1. State the uses of radioactivity in (a) medical field (b) industries (c) agricultural and scientific research.
  2. List the hazards of radioactivity.



  1. Whatisradioactivity?
  2. Whatisreproduction?
  3. Mention three benefitsofacquiringskills.
  4. Whatisozone layer depletion?
  5. Whatisreflection?



Basic Science for Junior Secondary School by J.O. Otugboyega et al. Page102-103



  1. ____ is referred to as the father of radioactivity. (a) Henri ford  (b) Pierre Currie (c) Marie Curie  (d) Albert Einstein
  2. Positively charged radiation that can be stopped by a thing sheet of paper is (a) X-ray (b) Beta particles  (c)  Alpha particles  (d) Gamma rays
  3. Blood moves out of the heart to the lungs through ____  (a) Aorta  (b) Pulmonary artery  (c) Vena Cava  (d) hepatic artery
  4. Which of the flowing is an electronegative element?   (a) Na (b) F  (c) Hg  (d) Au
  5. Which of the following is not a result of excess exposure to radiation? (a) HPV  (b) cancer  (c) Mutation in foetus  (d) Radioactive poisoning



  1. State five benefits of radioactivity.
  2. Should Nigeria embark on nuclear power as alternative source of electricity?  Give reasons for your answer. 

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