which of the following element of Group `17` shows radio-activity?

Options

A. Astatine
B. Iodine
C. Bromine
D. Chlorine

Answer

1

Explanation

Astiatine does not occur in nature ,But overtwenty artificial isotopes have been made.All of these are radiancetive,The most stable isotopes are `.^(210)At (t_(1//2)=8.3" hours")` and `.^(211)At (t_(1//2)=7.5" hours")`. The latter was first made in `1940` by a nuclear reaction in which `Bi` was bombarded with high energy `alpha` prticles:
`._(83)^(209)Bi+._(2)^(4) He rarr ._(85)^(211)At+2_(0)^(1)H`
Tracer methods were used to study the chemistry of `.^(211)At`, using minute quantities of about `10^(-14)` mole. This isotope decays by orbital element capture and by `alpha -`emission. At appears to resmble `I` quite closely.