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प्रश्न
How many α and β-particles are emitted in the transmutation \[\ce{^232_90Th -> ^208_82Pb}\]?
उत्तर
\[\ce{^232_90Th -> ^208_82Pb}\]
The emission of one α-particle decreases the mass number by 4 whereas the emission of β-particles has no effect on the mass number.
Net decrease in mass number = 232 - 208 = 24.
This decrease is only due to α-particles. Hence, number of α-particles emitted = `24/4 = 6`
Now, the emission of one α-particle decreases the atomic number by 2 and one β-particle emission increases it by 1.
The net decrease in atomic number = 90 - 82 = 8
The emission of 6 α-particles causes a decrease in atomic number by 12. However, the actual decrease is only 8.
Thus, the atomic number increases by 4. This increase is due to the emission of 4 β-particles.
Thus, 6 α and 4 β-particles are emitted.
