# How would you explain the atomic number of an element?

Jan 17, 2017

The $\text{atomic number, Z}$ is the number of protons, positively-charged.......
The $\text{atomic number, Z}$ is the number of protons, positively-charged, massive nuclear particles. And $Z$ defines the identity of the element:
Z=1, H; Z=2, He; Z=3, Li..........Z=23, V
You won't be asked to remember these numbers, because you should be issued a Periodic Table, which lists the atomic numbers and masses of all the elements exhaustively, in every exam in chemistry and physics you ever sit. You have to learn how to interpret the Table. For instance, given an isolated vanadium atom, $Z = 23$, how many electrons does it have? How many electrons does the vanadium ion, ${V}^{2 +}$ have? Why?