detailed solution

Correct option is B

The notation used for representing the mass number and atomic number of fluorine atom is ${}_9{}^{19}\mathrm{F}$.

The number of protons in an atom's nucleus is that element's atomic number. Since the number of protons present in a neutral atom of fluorine is 9, it can be said that the atomic number of fluorine is 9.

The sum of the number of neutrons and protons in the nucleus of an atom is its mass number.

Mass number of fluorine = 10 + 9 = 19

The numbers in superscript and subscript on the left-hand side of an element's symbol represent the atom's mass number and atomic numbers, respectively. Hence, the notation used for representing the mass number and atomic number of fluorine atom is ${}_9{}^{19}\mathrm{F}$.