Nuclear chemistry

The branch of science dealing with the study of nuclear reactions involving nuclear changes and their uses is called nuclear chemistry.

Radioactivity

The spontaneous process in which unstable nucleus become stable by emitting radiations such as α-particle, β-particle and γ-particle is called radioactivity.

Radioactivity element

The substance which emit invisible radiations α, β and γ are called radioactive substance and thus emitted radiations are called radioactive rays.

Characteristics of radioactive decays

1. The radioactive decay is unaffected by external pressure, temp, magnetic, electric field and high pressure etc.
2. The substance breaks up, leading to an irreversible self disintegration.

Nature of radioactive radiation

After the discovery of the phenomenon of radioactivity Rutherford investigated the nature of radiation emitted by a radioactive substance. He perform experiment in a pitch blende (lead box with a small hole). When radiation from the given radioactive sample was passed through two oppositely charged plates then the surface of photographic plate is affected at three positions.

a) Alpha rays

The radiations bending towards the −ve plate and positively charged called α-rays.

b) Beta particle

The radiation bending towards the +ve plate are negatively charged called β-rays.

c) Gamma rays

The third radiation pass straight forward are neutral called gamma rays.

Cause of radioactivity

Radioactivity occurs due to lack of stability of the nucleus.

Soddy Fajans Displacement Law

During radioactive process either α-particles is emitted or β-particle is emitted but not both simultaneously.

1) If α-particle is emitted

Its mass number is decreased by 4 and atomic no is decreased by 2.

2) If β-particle is emitted

Its mass no remains same but atomic no is increased.

For eg:

γ-particle emitted only after the emission of α and β-particle.

Types of radioactivity

1) Natural radioactivity

The spontaneous process in which unstable nucleus become stable naturally is called natural radioactivity.

Eg:

Some lighter isotopes show this phenomenon.

2) Artificial radioactivity or induced

The spontaneous process in which unstable nucleus become stable artificially is called artificial radioactivity.

Synthetic element

Those elements which don’t occur in nature and are produced in the laboratories by artificial transmutation are called synthetic element.

Synthetic element. units of radioactivity is Becquerel, curie and Rutherford.

Nuclear Rx’n

i) Nuclear fission rx’n

The process of splitting a heavy nucleus having mass number > 230 into lighter nuclei with release of large energy is called nuclear fission reaction.

ii) Nuclear fusion rx’n

The process of combining two or more light nuclei to form a stable heavier nucleus with release of a large amount of energy is called nuclear fusion rx’n.

Applications of radioactivity

• In the discovery of new fundamental particles and new elements.
• Medical applications.
• Industrial application.
• Medical diagnosis.
• Medical therapy.
• Prediction of the age.
• Agricultural application.

Harmful effects of nuclear radiation

• It destroys the skin.
• Lung exposure to α-radiation to lung cancer.
• β-particle cause the death of living organism.