Answer:
No, it hasn't. Because it has 9 protons and 10 neutrons and its average mass is 19, it has no common isotopes.
Explanation:
An isotope is an atom of the element which has the same atomic number (number of protons), but a different mass number. For example, hydrogen has 3 isotopes: H¹, H², and H³, all with an atomic number equal to 1.
The mass that is represented in the periodic table is the weighted average of the masses of the isotopes, based on the percentage that they're found in nature.
The mass of an atom is concentrated in the nucleus, so it is the mass of the protons plus the mass of the neutrons, which are equal to 1 amu (atomic mass unity).
For the fluorine atom with mass 19.00 and atomic number 9, we can infer it has 10 neutrons. Because the average mass is exactly 19.00 we can infer that all the fluorine atoms have 9 protons and 10 neutrons ( it's easy to observe in the periodic table that the masses are not exactly).
Then, we can infer for the information that fluorine has no common isotopes.