The term used for the number of protons in an atom is

• A. Atomic Mass
• B. Neutron Number
• C. Atomic Number
• D. Electron Count

Answer: (C)

The number of protons in an atom defines the identity of the element, and that count is called the atomic number. It is a unique identifier for each element and sits at the top of its periodic-table symbol as Z. In neutral atoms, the atomic number also equals the number of electrons, but ions can have different electron counts because they gain or lose electrons. Atomic mass, by contrast, is the total number of protons and neutrons in the nucleus, not just protons. The neutron number is simply the count of neutrons, which can vary among isotopes. The electron count is the number of electrons and can differ from the protons if the atom is ionized. So the term that correctly specifies the number of protons is the atomic number.