Question

How many neutrons are found in an isotope of F (Fluorine)?

Answer 1

For the calculation of the number of neutrons present in an atom we have to know about the Atomic number (${\text{Z}}$) of that atom as well as Atomic Mass (${\text{A}}$) of that atom, because atomic mass of an atom is the sum of number of neutrons and atomic number (${\text{Z}}$).

Complete answer: In chemistry many isotopes of fluorine are present but among them only ${}^{{\text{19}}}{\text{F}}$ isotope of fluorine is stable and found in $100\%$ abundant quantity.
-As we know that atomic number (${\text{Z}}$) of fluorine is $9$ and relation between atomic number and number of protons present inside the nucleus and number of electrons present in the atom is described as follow:
Atomic Number (${\text{Z}}$) = No. of protons = No. of protons
-From above given relation it is clear that:
Number of protons in Fluorine (F) atom = $9$
Number of electrons in Fluorine (F) atom = $9$
-Relation between Atomic mass (${\text{A}}$), number of neutrons and number of protons is described as follow:
Atomic Mass (${\text{A}}$) = No. of neutrons + No. of protons
-For ${}^{{\text{19}}}{\text{F}}$ isotope of fluorine atomic mass is $19$ and number of neutrons is calculated by rearranging the above equation as follow:
No. of neutrons = Atomic Mass (${\text{A}}$) - No. of protons
No. of neutrons in ${}^{{\text{19}}}{\text{F}}$ = $19 - 9 = 10$.
Hence, $10$ neutrons are found in an isotope of F (Fluorine).

Note:
Here some of you may think that in every isotope of fluorine only $10$ neutrons are present, but that assumption is wrong because here we were discussing only that isotope which is present in abundant quantity not about all isotopes.