What's the next in the series? H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Question

What's next in the following series - A) 3, 3, 5, 4, 4, 3, 5 ..., B) O, T, T, F, F, S, S, ...
(HINT - they are related)

Answer 1

Answer is Fm.
These are the chemical elements whose atomic numbers are perfect squares.

1, 4, 9, 16, 25, 36, 49, 64, 81, 100.