All atoms of a given element have the same ________.

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

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 while atoms of the same element have the same number of protons, they can have different numbers of neutrons, leading to different isotopes.
3. Note that atomic mass and mass number can vary among atoms of the same element due to the presence of isotopes.
4. Therefore, the property that is the same for all atoms of a given element is the number of protons.
5. Conclude that the correct answer to fill in the blank is 'number of protons'.