# The outer electronic configuration of radio active element present in 1A group is

$\begin{array}{1 1}(a)\;8s^1&(b)\;7s^1\\(c)\;5s^2&(d)\;6s^2\end{array}$

The outer electronic configuration of radio active element present in 1A group is $7s^1$
Hence (b) is the correct answer.