What subatomic particle determines the identity of an element in an atom?

The identity of an element in an atom is determined by the number of protons present in its nucleus. Protons are positively charged particles found in the nucleus, and each element on the periodic table is defined by its unique number of protons, known as the atomic number. For example, hydrogen has one proton, while carbon has six protons. This atomic number determines the chemical properties and behavior of the element, making protons the defining subatomic particles for identity.

Neutrons, while also located in the nucleus and contributing to the atomic mass, do not change the identity of the element; rather, they result in different isotopes of the same element. Electrons, which are negatively charged particles orbiting the nucleus, play a vital role in chemical reactions and bonding but do not define the element itself. The term "nuclei" refers to the plural form of nucleus and does not pertain to a specific subatomic particle that identifies an element. Therefore, protons are the key subatomic particles that determine an element’s identity.