How many alpha and beta particles are emitted when uranium `._(92)^(238)U` decays to lead `._(82)^(206)Pb` ?

Options

A. 10,8
B. 8,6
C. 8,8
D. 6,8

Answer

B

Explanation

When `""_92U^238 " decays to " ""_82Pb^206` , the mass number decreases by 238-206=32. When `beta` particles are emitted, there is no change in Abut when an a particle is emitted, A decreases by 4
`therefore` No. of `alpha` particles emitted = `32/4 = 8`
but these `8alpha` particles will decrease Z by `8x x2= 16` . Hence the atomic number (Z) of Pb should have been 92- 16 = 76, but it is given to be 82. This is possible by the emission by (82-76) = `6beta` particles. `6beta` particles will increase Z by 6. [Thus `alpha= 8, beta=6.` ]