In the simplified atomic model, what do all atoms of the same element have in common?

• A. The same mass number
• B. The same number of electrons at all times
• C. The same number of protons in the nucleus
• D. The same number of neutrons in the nucleus

Answer: (C)

Verified step by step guidance

1. Understand that an element is defined by its atomic number, which is the number of protons in the nucleus of its atoms.
2. Recognize that all atoms of the same element must have the same number of protons because this determines the element's identity.
3. Note that the mass number can vary among atoms of the same element due to different numbers of neutrons, leading to isotopes.
4. Remember that the number of electrons can change if the atom is ionized, so it is not always the same for all atoms of an element.
5. Conclude that the defining characteristic common to all atoms of the same element is the number of protons in their nucleus.