The atomic number is often referred to as the "fingerprint" of elements because it is a fundamental characteristic that uniquely identifies each element. It represents the number of protons found in the nucleus of an atom of that element.
Since the number of protons determines the element's chemical properties and its position in the periodic table, the atomic number serves as a distinguishing feature for different elements. No two elements have the same number of protons, so each element has a unique atomic number.
By knowing the atomic number of an element, one can determine its identity and infer various properties associated with that element, such as its atomic mass, electronic configuration, and chemical behavior. This uniqueness and consistency across all elements make the atomic number a useful and reliable identifier or "fingerprint" for elements in the realm of chemistry and physics.