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WAEC Physics 2016 Paper

Question : 44

Total: 47

^{198}_{79}\mathrm{Au} \leftarrow ^{198}_{80}\mathrm{Hg}

Solution:

Concept:

Beta emission changes the atomic number by 1 unit but leaves the mass number unchanged.

Explanation:

The decay involves mercury with atomic number

Z = 80

and gold with atomic number

Z = 79

So the change in atomic number is

80 - 79 = 1

The mass number remains

198

on both sides.

Since one beta particle changes the atomic number by one unit, only one beta particle is needed for this decay.

Answer:

One beta particle is emitted.

Correct option: A. 1

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