Another attempt:

On periodic table there is a continous route from potassium to silver:

K-Ca-Y-Hf-Ta-W(Y-2)-Re-Os-Ir-Pt-Au-Ag (au-ag is alpha squared)

We dont have a T in the image, so the answer is T.

Edit:

If s in Os does not count i can add scandium (Sc) in the route such as;

K-Ca-Sc-Y-....