Which of the following is closest to the average atomic mass of phosphorus (P) as listed on the periodic table?

• A. 30.97 u
• B. 35.45 u
• C. 28.09 u
• D. 32.07 u

Answer: (A)

Verified step by step guidance

1. Understand that the average atomic mass of an element is a weighted average of the masses of its naturally occurring isotopes, based on their relative abundances.
2. Identify the isotopes of phosphorus and their respective atomic masses and natural abundances (if given or known). For phosphorus, the most common isotope is \(^{31}\text{P}\) with an atomic mass close to 30.97 u and nearly 100% natural abundance.
3. Calculate the weighted average atomic mass using the formula: \[ \text{Average Atomic Mass} = \sum (\text{fractional abundance} \times \text{isotope mass}) \]
4. Since phosphorus has essentially one major isotope, the average atomic mass will be very close to the mass of that isotope, which is approximately 30.97 u.
5. Compare the calculated average atomic mass to the given options and select the value closest to 30.97 u.