The stable nucleus that has a radius `1//3` that of `Os^(189)` is-

Options

A. `Be^(9)`
B. `Li^(7)`
C. `F^(19)`
D. `C^(12)`

Answer

B

Explanation

Let nucleus be `""_(z)X^(A)`.
Nuclear radius, `R=R_(0)(A^(1//3))`
where `R_(0)` is a constant whose value of found to be `1.2xx10^(-15)m` and A is the mass number
`therefore" "(R_(X))/(R_(Os))=((A)/(189))^(1//3) rArr (1)/(3)=((A)/(189))^(1//3)`
`A=(189)/(3^(3))=(189)/(27)=7`
The given nucleus is `Li^(7)`.