(a) Briefly explain what would happen to a stable element if it is bombarded by \(\alpha\)-particles
(b) Explain how the bombardment of Uranium with neutrons could lead to nuclear fission chain reaction and hence nuclear explosion.
(c) State three characteristics of nuclear activity
(d) State three applications of atomic energy
(e) State two postulates of Bohr’s model of the atom and two limitations of such a model
Explanation
(a) If a stable element is bombarded by \(\alpha\) - particles the nucleus will become unstable and decay into other elements with the release of energy.
Example; \(^{14}_{7}N + ^4_2He \to ^{17}_8 O + ^1_1H\) + Energy
(b) When the nucleus of Uranium is bombarded with a neutron, it splits into two nearly equal parts with a release of energy and neutrons. These excess neutron, if not controlled, further bombard the remaining nuclei, causing a chain reaction and consequently an explosion, provided the critical mass of the Uranium is, exceeded
\(^{235}_{92}U + ^1_0U \to ^{236}_{92}U \to ^{141}_{56}Ba + ^{92}_{36}Kr + 3^1_0n\) + Energy
(c)(i) Radioactive substances give off identifiable radiation i.e \(\alpha, \beta\) and 8 radiations
(ii) They are chemically identical to their non-radioactive counterparts and later can be made radioactive by bombardment with nuclear particles
(iii) Radioactive materials decay with specific half-life.
(d) Three applications of atomic energy
(i) It is used for the production of nuclear weapons for warfare
(ii) It is used in the generation of electric power
(iii) It is used to detect leakages in underground pipes carrying oil or gases.
(e) Two Postulates of Bohr's Model of the Atom:
(i) Electrons occupy certain fixed orbits around the nucleus of an atom. When an electron is in one of these orbits it does not radiate any energy
(ii) The angular momentum is quantized in the allowed orbit.
Two Limitations To Bohr's Model:
(i) It could not interpret the details of the spectra of complex atoms
(ii) There is no theoretical basis for selecting the allowed orbits postulated.