What does the atomic number represent?

The atomic number is defined as the number of protons present in the nucleus of an atom. This is a fundamental property of an element, as it uniquely identifies that element and determines its position on the periodic table. Each element has a distinct atomic number, which means that the number of protons is what makes one element different from another.

In addition to identifying the element, the atomic number also affects the chemical properties of the element. Since atoms are neutral, the number of electrons usually equals the number of protons, meaning that the atomic number can also give insight into the electron configuration of the atoms involved. However, the atomic number specifically refers to protons, making this the correct choice in the context of the question.