Why is atomic number important?

Atomic number is one of the most important terms in the science of chemistry. Atomic number refers to numbers of protons in the nucleus of atom, and thanks to this number we can identify each chemical element and learn about its properties.

In chemistry atomic number is known under the symbol Z. Mass number (the total number of protons and neutrons in nucleus) has the symbol A, and this is the main reason why some people tend to mix these two numbers thinking that the symbol for atomic number is A. The number of neutrons in nucleus has symbol N.

The numbers of protons and neutrons doesn't have to be the same in the nucleus of an atom. Atoms that have the same atomic number Z but different neutron number N are known under the name of isotopes.

Atomic number is fundamental part of periodical law and one of the main foundations on which modern chemistry is built upon. The entire periodic table is arranged by means of atomic number because this offers the easiest solution to categorize chemical elements.


Atomic number is also important to determine the chemical properties of certain element. This is because neutral atoms have the same number of protons and electrons, so by knowing the atomic number you also know about the number of electrons, and electrons are the ones that make chemical bonds, therefore determining chemical properties of a given element.

The next time you look at the periodic table you'll know that the number listed for each element is its atomic number (A).