Which particle is distinguished by the number of protons in its nucleus?

The proton is the particle distinguished by the number of protons in its nucleus, as it is the defining characteristic of an element's atomic number. Each element on the periodic table is identified by its atomic number, which corresponds to the number of protons found in the nucleus of its atoms.

For instance, hydrogen, with one proton, has an atomic number of 1, while carbon, with six protons, has an atomic number of 6. This unique number of protons determines not just the identity of the element, but also its chemical properties, as the arrangement of electrons around the nucleus and the interactions they have with other atoms are largely influenced by how many protons are present.

In contrast, neutrons and electrons do not define the element itself; neutrons contribute to the atomic mass and can vary in number, leading to different isotopes of the same element, while electrons are involved in chemical interactions but do not affect the atomic number. Quarks, on the other hand, are the fundamental constituents of protons and neutrons; however, they are not the particles that directly determine the identity of an element. Thus, the proton uniquely serves as the key identifier of an atom's element based on the count of its protons