Which of the following is closest to the atomic mass of phosphorus (P)?

• A. 32.07 u
• B. 28.09 u
• C. 15.00 u
• D. 30.97 u

Answer: (D)

Verified step by step guidance

1. Understand that the atomic mass of an element is the weighted average mass of all its naturally occurring isotopes, measured in atomic mass units (u).
2. Recall that phosphorus (P) has an atomic number of 15, meaning it has 15 protons, and its atomic mass is close to the sum of protons and neutrons in its most common isotope.
3. Look at the given options and compare them to the known atomic mass of phosphorus, which is approximately 30.97 u.
4. Recognize that 32.07 u is close to the atomic mass of sulfur, 28.09 u is close to silicon, and 15.00 u corresponds roughly to the atomic number of phosphorus but not its atomic mass.
5. Conclude that the value closest to the atomic mass of phosphorus is 30.97 u, which matches the known standard atomic weight of phosphorus.