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  1. Magnetic Field | Week 1
    4 Topics
  2. Electromagnetic Field
    4 Topics
  3. Electromagnetic Induction
    6 Topics
  4. The Transformer
    5 Topics
  5. Simple A.C Circuit
    4 Topics
  6. Models of the Atom
    2 Topics
  7. Radioactivity
    3 Topics
  8. Half Life
    8 Topics
  9. Energy Quantization
    3 Topics
  10. Photoelectric Effect
    4 Topics
  11. Wave Particle Paradox
    3 Topics

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Lesson 7, Topic 2
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Radioactivity is the spontaneous decay or disintegration of the nucleus of the atom of a radioactive element during which radiations ( α, β and γ-particles) and energy are emitted 

Radioactive elements are elements that are capable of spontaneous decay with emission of radiation and energy. Examples of such elements are uranium, boron, thorium, radon, cobalt, radium.

Properties of Radioactive Radiations

α-particles β-particlesγ-particles
1.effect of electric fielddeflected towards the –ve plateDeflected towards the +ve plateUnaffected
2.Effect of magnetic fieldDeflected toward the south poleDeflected towards the north poleUnaffected
3.Nature of chargePositively chargedNegatively chargedNeutral
4.MassMassive (heavy)Less massiveNo mass
5.MomentumHigh momentum Low momentum No momentum
6.Penetrating powerLow penetration powerHigh penetration powerVery high penetration power

Nature of the atom 
Ionization power
Helium nucleus

High ionization power
High energy electrons
Low ionization power
Electromagnetic radiation of short wavelength
No ionization 

Types of Radioactivity

There are two types of radioactivity namely natural radioactivity and artificial radioactivity.

Natural radioactivity is the splitting or breakdown of nuclei of elements on their own without any stimulation from man, during which α-particles,  β -particles,  γ-ray, or combination of any of these with accompanied energy.

Artificial radioactivity – this is achieved by bombarding ordinary materials with radioactive particles to give radioactive elements radiation and energy. E.g.

\( \scriptsize _{13} ^{27} \textrm {Al} + \; _{2} ^{4} \textrm {He} \rightarrow \; _{15} ^{30} \textrm {P} + \; _{0} ^{1} \textrm {n} \rightarrow \; _{14} ^{30} \textrm {S} + \; _{1} ^{0} \textrm {e} + energy\)

When an aluminum is bombarded with helium or alpha particles, it gives rise to unstable phosphorus nuclei (radioactive phosphorus) which disintegrates further spontaneously into stable silicon atoms

Neutrons, protons and alpha particles are used as very effective bombarding particles for disintegrations of nuclei of elements.

Radioisotopes are isotopes made artificially by bombarding neutrons or proton or deuterons at elements 

Radioactive elements are elements that spontaneously emit radiation from their nucleus e.g. radium, uranium, radon.


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