Question

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

Answer 1

Hint: 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 $100\mathrm{\%}$ 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.