# How do atomic numbers work?

The atomic number, $Z$, is the number of protons, massive, positively charged nuclear particles that define the identity of the element.
If $Z$ $=$ $1$, the element is hydrogen; if $Z$ $=$ $2$, the element is helium; if $Z$ $=$ $3$, the element is lithium; .....................if $Z$ $=$ $31$, the element is gallium.
$Z$ gives also the number of electrons in the neutral element. You do not have to remember these. In every exam you ever sit in Chemistry or Physics, you should be supplied with a Periodic Table of Elements.