Artificial transformation is induced in an element by irradiation (exposure to radiation) either by accident or by intent) . It was first achieved by Rutherford. An ordinary material not normally radioactive is made radioactive by bombarding it with radioactive particles e.g
42He + 27 13Al → 3015 P + 10n
The protons and neutrons (nucleons) in the nucleus of each atom are held together by very powerful nuclear forces. An enormous amount of energy is required to tear the nucleon apart. Enrico Fermi (1934) discovered that the nucleus can be split by bombarding it with a slow neutron.
10n + 23592U ARTIFICIAL TRANSFORMATION 14156Ba + 92 36Kr + 3 10n + energy.
He discovered that the total mass of the component products is less than the mass of the original materials. The difference in mass (mass defect) is a measured of the nuclear energy released.According to Albert Einstein
E = ∆ mc2
E = nuclear energy
∆m = mass defect
c= velocity of light ( 3.0 x 108ms-1)
This is the splitting up of the nucleus of a heavy element into two approximate equal parts with the release of a huge amount of energy and neutrons.
Fission occurs with most of the massive nuclei. When the heavy nucleus is bombarded by slow neutron, several neutrons are produced as by –products.
These neutrons may cause the splitting of other nuclei, which in turn yield more neutrons which may further split other nuclei and so on.Thus a chain reaction is set in motion
A chain reaction is a multiplying and self maintaining reaction . When the size of the nuclei exceeds a certain critical mass, there is a rapid production of neutron accompanied by a release of tremendous amount of energy in a nuclear explosion. This is the principle of the atomic and nuclear fission bombs. It is also the process used in the present day nuclear power station .
This is a nuclear process in which two or more light nuclei combine or fuse to form a heavier nucleus with the release of a large amount of energy e.g.
21H + 31H → 41 He + 10n + energy
To bring the two lights nuclei together in a fusion process, very high temperature of the order 10,6000C are required to overcome the coulomb repulsive forces between the two nuclei.
ADVANTAGES OF FUSION OVER FISSION
- Fusion is more easily achieved with lightest element e,g hydrogen.
- The raw materials required from fusion are more readily and cheaply available
- Fusion process produces less dangerous by-products.
Peaceful uses of nuclear energy
- Many nuclear power plants are now being used to generate electricity
- Several fission products obtained in nuclear reaction are used for radiotherapy.
- Radio isotopes from nuclear plants are used in agriculture as tracers and preservatives.
- some space crafts. Ships and submarines are powered by nuclear energy.
- Define the following terms (a) Conduction (b) Convection (c) Radiation
- With the aid of a diagram, explain how the construction of a thermos flask minimizes heat exchange with the surrounding.
1. If a nucleus 31H decays, a nucleus of 32H is formed accompanied with the emission of (a) beta particles (b) gamma particle (c) alpha particle (d) x-rays.
2. The count rate of radioactive substances diminishes from 600 to 150 in 60 secs. Determine the half life of the substance (a) 15 secs (b) 30 secs (c) 45 secs (d) 60secs.
3. a radioactive substance half life of 20hrs. what fraction of the original radioactive nuclide will remain after 80hrs (a) 1/32 (b) 1/16 (c ) 1/8 (d) 15/16
4. a material of mass 1.0X10-3kg undergoes fission process which decreases its mass by 0.02%. calculate the amount energy released in the process [c=3X108m/s]
(A) 1.8X1020J (B) 1.8X1013J (C) 1.8X1011J (D) 1.8X1010J
5. In a nuclear reaction the mass defect is 2.0X10-6g. Calculate the energy released, given velocity of light is 3X108m/s. (A) 9.0X1007J (B) 1.8X1008J (C) 1.8X1009J (D) 9.0X10‑10J
1. Explain the terms nuclear fission and nuclear fusion
2. Nuclear reaction is given by the equation 2 1H + 31H → 42H + 10n + energy
(a) What type of nuclear reaction is it?
(b) state two component in a nuclear reactor used to control chain reaction