Question

question 2 of 10
which of the following correctly compares the phosphorus isotopes 31p and 32p?
a. 31p has 31 protons, whereas 32p has 32 protons.
b. 31p has 31 neutrons, whereas 32p has 32 neutrons.
c. 31p has 16 neutrons, whereas 32p has 17 neutrons.
d. 31p has 16 protons, whereas 32p has 17 protons.

Explanation:

Step1: Recall the atomic number of phosphorus

The atomic number (\(Z\)) of phosphorus (\(P\)) is 15. This means the number of protons in both \(^{31}\text{P}\) and \(^{32}\text{P}\) is 15. So options A, B, and D (which have incorrect proton - number claims) can be eliminated.

Step2: Use the formula for the number of neutrons

The formula for the number of neutrons (\(N\)) is \(N = A - Z\), where \(A\) is the mass number.
For \(^{31}\text{P}\), \(A = 31\) and \(Z = 15\). Then \(N=31 - 15=16\).
For \(^{32}\text{P}\), \(A = 32\) and \(Z = 15\). Then \(N = 32-15 = 17\). So option C is correct.

Answer:

C. \(^{31}\text{P}\) has 16 neutrons, whereas \(^{32}\text{P}\) has 17 neutrons.