# What is the atomic number of an element defined as?

$\text{The atomic number, Z........}$
$\text{The atomic number, Z,}$ is the number of protons, massive, positively charged, present in the nucleus. $Z$ defines the identity of the element: Z=1,"hydrogen";Z=2,"helium";Z=3,"lithium";
$\ldots \ldots \ldots \ldots \ldots . . Z = 23 , \text{vanadium}$.