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?

1 Answer
Oct 19, 2015


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


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"#.