Which of the following is likely to be least stable?

Options

A. `._(20)^(40)Ca`
B. `._(25)^(55)Mn`
C. `._(50)^(119)Sn`
D. `._(13)^(30)Al`

Answer

d

Explanation

`._(20)^(40)Ca, ._(25)^(55)Mn, ._(50)^(119)Sn, ._(13)^(30)Al`
`(n)/(p), (20)/(20) = 1 (30)/(25) = 1.2, (69)/(50) = 1.38, (17)/(13) = 1.31`
All are stable according to n/p rule but experimental observations confirm that `._(13)^(30)Al` is radioactive with half lfie of 3.7 sec