Question

If ₉₂U²³⁸ changes to ₈₅At²¹⁰ by a series of α and β decays. The number of α and β decays undergone is

• A. 7 and 5
• B. 7 and 7
• C. 5 and 7
• D. 7 and 9

Answer 1

The correct option is B

7 and 7

Let number of α-decays are x and number of β-decays are y. Then
92-2x-y=85
Or 2x-y=7
and 238 - 4x =210
x=7
Substituting this value in Eq.(1). We get

y=7