The subatomic particle that determines the identity of an atom is the proton.

Quick Scoop

  • The number of protons in an atom’s nucleus is called its atomic number , and this number defines which element it is (hydrogen has 1 proton, helium has 2, carbon has 6, etc.).
  • If you change the number of protons, you change the element itself (for example, turning carbon into nitrogen), so protons are what fix an atom’s identity.
  • Neutrons and electrons can change without changing the element:
    • Different numbers of neutrons give isotopes of the same element.
* Different numbers of **electrons** give ions of the same element.

In forum-style homework and quiz discussions, when people ask “which subatomic particle determines the identity of an atom,” the accepted answer is consistently “proton.”

TL;DR: The identity of an atom (which element it is) is determined by the number of protons in its nucleus, also known as its atomic number.

Information gathered from public forums or data available on the internet and portrayed here.