What is the term for the number of protons found in the nucleus of an atom?

The number of protons in the nucleus of an atom is known as the atomic number. This fundamental aspect of an atom defines not only the element itself but also its chemical properties. Each element has a unique atomic number, which can be found on the periodic table. For instance, hydrogen has an atomic number of 1, while carbon has an atomic number of 6.

The atomic number is crucial because it determines the identity of the element; changing the number of protons would change the element entirely. Other terms, such as mass number, molecular weight, and isotope count, relate to different characteristics of atoms but do not specifically refer to the count of protons. Mass number refers to the total number of protons and neutrons in the nucleus, molecular weight pertains to the mass of molecules, and isotope count refers to the variety of isotopes an element can have, which is based on varying neutron numbers, not protons.