What is the definition of atomic number

it decides where a element will be placed in the periodic table, it also tells you how many protons in a nucleus, and it tells u the chemical property of an element

The number of protons in the nucleus of an atom, which determines the chemical properties of an element and its place in the periodic table.

The total number of protons present in the nucleus of an atom represents the atomic number of a particular atom. Every atom of a particular element is composed of the same number of protons and therefore have the same atomic number.