If an element has atomic number 9 and atomic mass 19, how many neutrons will it have?

2 Answers
May 3, 2017

TEN neutrons.........


To an excellent approximation, atomic mass is equivalent to nuclear mass; i.e. the combined mass of neutrons and protons. Can you tell us the identity of the nuclide? You have all the info necessary to do so.

May 11, 2017

10 neutrons.


We know that Mass number #~~# Atomic mass of an atom(as electrons weigh almost nothing relative to an atom, although each of them have mass of #9.11 * 10^-34# kg. );
Mass Number = Number of Protons + Number of Neutrons;
And Atomic Number = Number of Protons.

So Number of Neutrons = Atomic Mass - Atomic Number = 19 - 9 = 10
This explains the answer.