Define $Z$,$A$,and $N$ by describing the structure of an atom.

(N/A) An atom consists of a central nucleus surrounded by electrons. The nucleus is composed of protons and neutrons.
$1$. $Z$ (Atomic Number): It is defined as the total number of protons present in the nucleus of an atom. It determines the identity of the element.
$2$. $A$ (Mass Number): It is defined as the total number of protons and neutrons (collectively called nucleons) present in the nucleus of an atom. $A = Z + N$.
$3$. $N$ (Neutron Number): It is defined as the total number of neutrons present in the nucleus of an atom. It is calculated as $N = A - Z$.