* The atomic number of the element? This will tell us the number of protons, which is the same as the number of electrons in a neutral atom.
* Is it an ion? If so, is it positively or negatively charged? This will tell us if the number of electrons has changed from the neutral atom.
For example:
* Titanium (Ti) has an atomic number of 22, meaning a neutral titanium atom has 22 electrons.
* Scandium (Sc) has an atomic number of 21, but if it loses one electron to become a +1 ion (Sc¹⁺), it will have 20 electrons.
Please provide more information so I can give you a more accurate answer!