What particle determines the atomic number of an element and carries a positive charge?

The atomic number of an element is determined by the number of protons it contains in its nucleus. Protons are positively charged subatomic particles, and this positive charge is crucial because it affects how the element interacts with other atoms and defines its chemical identity. The atomic number not only indicates the number of protons but also determines the position of the element on the periodic table. Each element has a unique atomic number, which corresponds to the number of protons; for example, hydrogen has an atomic number of 1, meaning it has one proton, while carbon has an atomic number of 6, indicating six protons.

While neutrons are neutral and help contribute to the mass of the atom, they do not influence the atomic number. Electrons, which carry a negative charge, exist in orbitals around the nucleus and balance out the positive charge of protons but do not define the element's atomic number themselves. Mass numbers, on the other hand, relate to the total number of protons and neutrons in an atom's nucleus, rather than specifically identifying the number of protons alone. Therefore, the role of protons is pivotal in recognizing the atomic structure and characteristics of an element, making it the correct choice in this question.