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Physics

Transformation of Elements

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

The phenomenon of radioactivity was first discovered by Henri Becquerel

Natural radioactivity is the spontaneous disintegration of the nucleus of an atom during which α-particle or β-particle, or gamma rays or a combination of any or all the three and heat (or energy) are released.

When a radioactivity element undergoes radioactive decay, it may emit either α-particle, β-particle or γ rays. This changes the atomic number of the element, hence a new element is formed. For example, Radium-226 decays by emitting an α-particles to turn into a new element Radon. Radium-226 has a mass number 226 and an atomic number 88 and hence it is denoted by 22688Ra. The α-particles it emits is a Helium nucleus denoted by 42He. So when Radium 226 emits an α-particle. We can write a nuclear equation:

22688Ra → 42He + 22286Rn + energy

(Radon – 222)

Radon – 222 decays to Radium – 222 by emitting 2 β-particles. When the nucleus of an atom emits a β-particle (i.e. an electron), the atomic number of the atom increases by one unit, but its mass number remains unaltered. Hence since two β-particles are emitted from Radon 222 we can write the equation

22286Rn → 2 0-122288 Ra + energy

Uranium-238 decays by emitting two α-particles and two β-particles to thorium -230. Hence we can write the nuclear equation thus:

23892U → 2 42H + 2 0-1e + 23090Th + energy

↑           ↑

2α-particles 2β-particles

Thorium-234 decays by emitting a β-particle to the element Protactinium-234 thus:

23490 Th→ 0-1e ­23491Pa + energy

Generally we represent alpha (α) decay by

ABX→42He + (A-4)(z-2)Y

α-particle

and Beta (β)-decay by AZX→ 0-1e ­A(Z+1)Y

Β-particle

Gamma radiation (γ) is a form of light, emitted as photons of energy hf, and has zero mass number and zero charge (A = 0, Z = 0).

To balance a nuclear equation we ensure that the sun of the atomic numbers, Z (subscripts) must be the same on the two sides of the equation. Also the sum of the mass numbers A (superscripts) must be the same on the two sides of the equation.

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