Which property of an atom determines the element to which it belongs?

• A. The atomic mass of the atom
• B. The number of neutrons in the nucleus
• C. The number of protons in the nucleus
• D. The number of electrons in the outer shell

Answer: (C)

Verified step by step guidance

1. Understand that an element is defined by a unique characteristic of its atoms, which distinguishes it from other elements.
2. Recall that the atomic number of an atom is the number of protons in its nucleus, and this number is unique for each element.
3. Recognize that while atomic mass depends on both protons and neutrons, it can vary due to isotopes and does not define the element itself.
4. Note that the number of neutrons can vary within atoms of the same element (isotopes), so it does not determine the element.
5. Understand that the number of electrons can change due to ionization, so it also does not define the element; therefore, the defining property is the number of protons in the nucleus.