Question

the atomic mass of fluorine is 18.998 amu and its mass spectrum shows a large peak at this mass. the atomic mass of chlorine is 35.45 amu, yet the mass spectrum of chlorine does not show peak at this mass. Explain the difference.

Answer 1

Do you know how a mass spectrometer works, more or less?

Answer 2

The question itself is misinforming you, atomic mass of fluorine is 18.998 amu (1 atom) but the atomic mass of chlorine is \(\color{red}{NOT}\) 35.45 amu, thats the mass of dichlorine 2 atoms of chlorine (\(Cl_2\)).