All atoms of the element vanadium must have the same:

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

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 changing the number of protons changes the element itself.
3. Note that the mass number (sum of protons and neutrons) can vary among atoms of the same element, resulting in different isotopes.
4. Know that the number of neutrons can vary in atoms of the same element, which also leads to isotopes with different mass numbers.
5. Remember that the number of electrons can vary if the atom is an ion, so electrons are not fixed for all atoms of an element.