The sodium atom contains 11 electrons, 11 protons, and 12 neutrons. What is the mass number of sodium?
We have the
A sneakier question would have asked:
The sum of neutrons and protons, the massive nuclear particles, gives the mass number, with which we often label the elemental symbol as a left hand superscript. But the number of
It is not too difficult to incorporate these ideas into your understanding, and if you have a Periodic Table in front of you (and you should have one NOW!) these problems are straightforward.