Question

If an atom has an atomic number of 9 and an atomic mass number of 19, how many protons, neutrons, and electrons does it have?

Answer 1

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 `""_9^19"F"`.