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

I presume you have the atomic number, $Z$, of the element.
If you have $Z$, the number of massive, positively charged particles in the nucleus, then you automatically have the number of electrons. Why?
Because matter, all matter, is electrically neutral to a first approximation. So if your element is neutral, and you know $Z$, then the number of electrons is the same.