SS3 First Term Chemistry Lesson Note – Nuclear Chemistry

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WEEK 4:

TOPIC: NUCLEAR CHEMISTRY

CONTENTS:

1. Radioactivity
2. Types and nature of radiations
3. Differences between chemical and nuclear reaction
4. Half-life and applications of radioactivity

PERIOD 1: RADIOACTIVITY

This is a spontaneous decay of unstable nuclei with the release of energy and radiation such as alpha particle, Beta particle and gamma ray. Radioactivity was discovered by A.B Becquerel in the year 1896 when he found that a sample of uranium could affect the photographic plate even after it had been wrapped in black so as to prevent it fluorescence from reaching the photographic plate.

After uranium had been shown to have this property, there had been other experiments to identify other material of similar behaviour. Other radioactive materials that had been discovered include: radium, thorium, polonium … had been discovered. They exhibit the following properties:

1. They affect photographic plate
2. They ionize gas
3. They produce fluorescence

The ionizing effect of radioactive material can be observed using a charge electroscope. The electroscope discharge when a radioactive material is brought its cap. This is because radiation emitted by the material causes ionization (produce electrons which discharge the electroscope).

Radioactive elements

These are elements that undergo disintegration spontaneously emit radiation and particles. Example include; radon, radium, uranium and polonium.

A form of radioactivity which occur spontaneously without doing anything to initiate it nor can anything be done to control it is called NATURAL radioactivity.

A form of radioactivity that is induced in element that would have otherwise being stable is called induced or ARTIFICIAL radioactivity.

Artificial radioactivity is induced by bombarding stable nuclei with fast moving ions such proton or alpha particles. Artificial radioactivity is induced in device called accelerators. Example include: cyclotron, linear accelerator, Van de Graff accelerator.

PERIOD 2: TYPES AND NATURE OF RADIATIONS

There are three main types of radiation emitted from radioactive materials:

1. Alpha particle
2. Beta particle
3. Gamma ray

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