An element's mass number is the number of protons plus the number of neutrons.
If we have the mass number and the atomic number of an element, we can find the number of protons, neutrons and electrons that element has:
Argon has an atomic number of 18 and a mass number of 40.
The atomic number is 18 so it has 18 protons.
Atoms have the same number of electrons as protons so it also has 18 electrons.
The mass number (protons + neutrons) is 40. We know there are 18 protons, so the number of neutrons is 40 - 18, which is 22. There are 22 neutrons.
Comments
No comments have yet been made