1.

The number of a-particles emitted by ""^(218)Ra in changing to stable isotope ""^(206)Pb is :

Answer»

3
4
6
2

Solution :`_(84)^(218)Rato_(82)^(206)Pb++x""_(2)^(4)He+y""_(-1)overset(0)E`
Comparing MASS NUMBERS
`218=206+4x+0`
4x=12 or x=3


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