Gone Fission

Explanation: The three elements in the grid (10A, 23A, 37A) can be spelled using chemical symbols- 10A= Ar (Argon), Se (Selenium), Ni (Nickel), C (Carbon). 23A= Ti (Titanium), N (Nitrogen). 37A= Si (Silicon), Li (Lithium), Co (Cobalt), N (Nitrogen). The atomic numbers (yes, I went there) for these elements, in order, are 18, 34, 28, 6, 22, 7, 14, 3, 27, 7. The corresponding grid numbers spell the answer- NUCLEAR ERA. (I used cobalt instead of carbon and oxygen ‘cause it worked better)

Thank you! I figured it out from the title and prompt, but I am eager to find out the actual metanism. (All I noticed so far was the double letters.)

Oh, dear! I knew the periodic chart would be used somehow, but couldn't find much beyond Ar and Sn and Si RRC(Ar) and (Sn)O and (Si)DE and a bunch of other "hidden" elements like A(Pb) or (Al)Y or I(Cu)... Great idea, but sorry I just couldn't see it.