How would you determine the total number of electrons found in an atom?
You would look up the atomic number,
To a firat approximation all matter, and thus all elements, are neutral.
For every positively charged nuclear there MUST be a negatively charged EXTRA-NUCLEAR particle, i.e. an electron, conceived to whizz about the nuclear core.
Of course, elements can form ions, with a net charge defined by the excess or deficiency of electrons with respect to the atomic number