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Q.
In a radioactive reaction $ _{92}{{X}^{232}}{{\to }_{82}}{{X}^{204}} $ the number of $ \alpha $ -particles emitted is:
Bihar CECEBihar CECE 2005
Solution:
$ \alpha - $ particle is a nucleus of helium atom and its symbol is $ 2\,He{{\,}^{4}}. $
When an $ \alpha - $ particle is emitted from a nucleus, the resultant nucleus reduces in mass number by 4 link and in atomic number by 2 unit.
Loss in mass number $ =232-204=28 $
Therefore, number of $ \alpha - $ particles emitted
$ =\frac{28}{4} $
$ =7 $