An atom of an unknown element contains 17 protons and 19 neutrons. The total number of electrons present in a neutral atom of this element is

This isotope of fluorine has 9 protons, 9 electrons and 10 neutrons.

Explanation:

The atomic number is the number of protons  ( p + ) . In a neutral atom, the number of electrons  ( e − )  equals the number of protons. Mass number is the sum of the protons and neutrons  ( n 0 )  of a particular isotope. If you have mass number and atomic number, subtract the atomic number from the mass number to get the number of neutrons.  ( Mass number ) − ( atomic number ) = number of neutrons .

There are:

9 protons

9 electrons

10 neutrons

Fluorine is the element in question, as its atomic number is  9 . You would name this particular isotope using the mass number. It would be called fluorine-19.

The nuclear or isotopic notation would be  19 9 F