Neutral atoms of all isotopes of a given element have the same:

• A. mass number
• B. number of neutrons
• C. atomic mass
• D. number of protons

Answer: (D)

Verified step by step guidance

1. Understand the definitions of the terms involved: the mass number is the total number of protons and neutrons in the nucleus; the number of neutrons varies among isotopes; the atomic mass is the weighted average mass of all isotopes of an element; the number of protons defines the element itself.
2. Recall that isotopes of an element have the same number of protons but different numbers of neutrons, which means the mass number and number of neutrons can differ among isotopes.
3. Recognize that the atomic mass is an average value that depends on the relative abundance of each isotope, so it is not the same for all isotopes individually.
4. Conclude that the only property that remains constant for all neutral atoms of all isotopes of a given element is the number of protons, which is also called the atomic number.
5. Therefore, the correct answer is that neutral atoms of all isotopes of a given element have the same number of protons.