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CHEMISTRY

TOPIC: Nuclear Chemistry - 1

By Kingsley Idiagbor, B.Sc(Hons),PGDCs,NCE,MNSM


Natural Radioactivity

This is the spontaneous or sudden emission of radiation by an element with unstable atomic nuclei. Such an element is said to be radioactive.

Types of Radiation

There are three major types of radiation emitted by a radioactive element and include:

  • Alpha ( a) particles;
  • Beta (b ) particles and
  • Gamma (g ) rays

The table that follows, shows the characteristics of the listed radiations:

Properties Alpha (a ) particles Beta (b ) particles Gamma (g) rays
Nature Helium nuclei; 42He Electrons; 0 -1e Electromagnetic radiations with very short wavelength
Electric charge +2 -1 no charge
Mass 4 units 1/1840 (very negligible) no mass
Velocity 1/20 of the speed of light varies the speed of light
Relative penetration 1 (very low); can be absorbed by a thin paper or few cm thickness of air. 100 (moderate);

can be absorbed by metallic foil.

 10,000 (extremely high); can only be stopped by a thick lead block.
Degree of deflection in electric and magnetic fields slightly deflected towards the negative plate strongly or markedly deflected towards positive plate. No deflection; neither affected by electric nor magnetic fields.
Ionizing power very high;

of the three types of radiation, it has the strongest ionizing effect.

 Moderate;

it is less than that of alpha particles

 very low.


Types of Radioactive decay

Alpha () decay:

This is the emission of alpha particle leading to a reduction in the mass number of the radioactive element by 4 and atomic number by 2.

E.g.



Beta ( ) decay.

When this occurs, there is emission of beta particles with no effect on the mass number of the element. However the atomic number is increased by 1.




K-capture (or positron emission)

This occurs in rare situations where there is unequal number of proton and neutrons with the effect that one of the electrons is converted to neutron in order to stabilize the nucleus.




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