What represents the number of protons in an atomic nucleus?

The atomic number is a fundamental property of an element that directly represents the number of protons in the nucleus of its atoms. This number is unique to each element and determines its position on the periodic table. The atomic number not only indicates the identity of the element but also plays a crucial role in determining its chemical behavior and properties.

For example, hydrogen has an atomic number of 1 because it has one proton, while carbon has an atomic number of 6, indicating it has six protons in its nucleus. The atomic number is essential for understanding how elements combine and react chemically.

In contrast, mass number refers to the total number of protons and neutrons in an atomic nucleus, making it distinct from the atomic number. Atomic weight is a weighted average that reflects the mass of an element's isotopes in relation to the mass of carbon-12, and it is not solely based on the number of protons. Molecular weight pertains to the mass of a molecule, which considers the combined atomic masses of its constituent elements. Each of these terms has its significance, but the atomic number specifically measures the proton count, solidifying its importance in identifying elements.