Which subatomic particle determines the identity of an element (i.e., its atomic number)?

• A. Alpha particles
• B. Protons
• C. Electrons
• D. Neutrons

Answer: (B)

Verified step by step guidance

1. Understand that the identity of an element is defined by its atomic number.
2. Recall that the atomic number is the number of protons in the nucleus of an atom.
3. Recognize that protons carry a positive charge and are unique to each element, distinguishing one element from another.
4. Note that electrons and neutrons do not determine the element's identity: electrons affect charge and chemical behavior, while neutrons affect isotope variation.
5. Conclude that the subatomic particle determining the identity of an element is the proton.