In comparison to an atom of 199F in the ground state, an atom of 126C in the ground state has

You have to convert 199F into Celsius to make a comparison. It has the equation of (T (F) - 32) / 1.8. so,

T (C) = (T (F) - 32) / 1.8

T (C) = (199F) - 32) / 1.8

T (C) = 92.78C

The atom at 126C is more reactive than the atom at 199F.