# How many electrons are there in the strontium atom?

For strontium, $Z = 38$. And thus in a strontium nucleus, there are 38 massive, positively charged particles, 28 protons (this is what defines the atom as strontium), and around the nucleus there are NECESSARILY 28 negatively charged particles that we call electrons are conceived to whizz about. There must be equal numbers of these particles because here the atom was electronically neutral. What about rubidium, what about krypton?