Nuclear Chemistry: 

An atom contains nucleus where protons and neutrons are present, and the electrons revolve round the nucleus in definite orbits. The nucleus of an atom has no role in a chemical reaction. Chemical reactivity is decided by the number of valence electrons.

But there are process like radio activity and artificial transmutation where the atomic nucleus is involved. Nearly the whole mass of the atom is concentrated in the nucleus.

Discovery of radioactivity

French scientist Henry Becquerel wrapped some uranium salt in a paper and placed it on a photographic plate wrapped in black paper. He found that the photographic plate was blackened.The same effect was caused by Thorium. Uranium and thorium emitted a kind of rays which penetrated the paper there by the photographic plate was affected.

Later Madam Curie isolated a substance from pitchblende which emits rays which were 400 times more powerful rays than the rays emitted by uranium. It was named as polonium. Then . she found Radium which 900 times more powerful in its radiation. The radio active substances emit alpha, beta and gamma rays.

When an alpha particle is emitted (helium nucleus) the parent element loses 2 units of atomic number and 4 units of mass number and produces a daughter element.

                                               ₉₂U²³⁸ ----------- ₉₀ Th²³⁴ + ₂ He⁴ (alpha particle)

The above equation is alpha decay. So in the periodic table thorium will occupy two groups left to uranium.

Beta emission

Emission beta particle does not affect the mass number but increase the atomic number or positive charge by one unit. So daughter element will have the same mass number of the parent element. But has one more of atomic number.

                                                        ₉₀Th ²³⁴ ---------- ₉₁ Pa²³⁴ + _-1 e⁰

Since the daughter element has atomic number one more than the parent element in periodic tablr it is found one group to the right of the parent element.

Gamma radiation does not produce a different element as it is not made of any particle, but every alpha and beta radiation is accompanied by gamma radiation. The cause of radio activity. An unstable nucleus is the cause of radioactivity. The instability of the nucleus is decided by the neutron proton ratio.

Maximum stability is there when N=Z N is neutron and Z is proton

Nuclear fission

It involves splitting up of heavy nucleus into lighter nuclei. It is a chain reaction.. High temperatureis not required to start the reaction. Nuclear waste is produced.

Nuclear fusion

It involves the union of two or more lighter nuclei to form heavy nucleus.

It is not a chain reaction High temperature is needed to start the reaction. very difficult to be carried out in a reactor to prodice energy. No nuclear waste occurs.

Applications of radio activity

Gamma rays emitted by the radio isotopes can be used for the treatment of cancer. It is used to arrest the growth of cancerous cells and also to destroy them In agriculture the uptake of phosphorus by plants is studied by mixing radio active phosphorus with phosphoric fertilizers.In chemistry it is used to find the solubility of sparingly soluble salt. To find if blood is circulating to a wound or not a radio active isotope is injected into the blood stream.