How do you find the number of electrons in an element/ion?

Question

If you have the number of protons and neutrons how do find the number of electrons?

Thanks.

Answer 1

The number of protons (the atomic number) defines what element it is. If there are Z protons, and the charge of the ion is "C", then the number of electrons is:
E = Z - C

So, if we have a -2 oxygen ion, it has 8 protons (Z = 8), and
E = Z - C
E = 8 - (-2)
E = 8 + 2
E = 10 electrons

The neutrons are not important when describing ions.

Answer 2

First look at the number of protons it has - use that as your starter. If something is simply an element, the number of protons = number of electrons.


If it is an ion then it is "charged" by extra or less electrons, so then look at what type of ion it is (ie +1, -2, etc). if it is -1 it has one extra electron (because electrons are negatively charged) if it is has -2 it has two extra electrons...... if it is +1 has one less electron if it is +2 has two less electrons


Hope that helps

Answer 3

# of electron = # of proton - electronic charge