Periodic Table And Periodicity

\(\text { Given below and the atomic masses of the elements: }\)

$$ \begin{array}{|l|l|l|l|l|l|l|l|l|l|} \hline \text { Element: } & \mathrm{Li} & \mathrm{Na} & \mathrm{Cl} & \mathrm{~K} & \mathrm{Ca} & \mathrm{Br} & \mathrm{Sr} & \mathrm{I} & \mathrm{Ba} \\ \hline \text { Atomic Mass }\left(\mathrm{g} \mathrm{~mol}^{-1}\right): & 7 & 23 & 35.5 & 39 & 40 & 80 & 88 & 127 & 137 \\ \hline \end{array} $$

\(\text { Which of the following doesn't form triad? }\)