All phosphorus atoms have the same:

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

Answer: (B)

Verified step by step guidance

1. Understand that an atom is defined by its number of protons, which is called the atomic number. This number is unique to each element and does not change for atoms of the same element.
2. Recognize that the number of electrons in an atom can vary if the atom is an ion, so electrons are not always the same for all atoms of an element.
3. Know that the number of neutrons can vary among atoms of the same element, resulting in different isotopes. Therefore, neutrons are not necessarily the same for all phosphorus atoms.
4. Atomic mass is the weighted average of all isotopes of an element and can vary depending on the isotope distribution, so it is not the same for all phosphorus atoms.
5. Conclude that the only quantity that is the same for all phosphorus atoms is the number of protons, which defines the element phosphorus.