The correct option among the provided choices is A: an atomic number of 32.
Phosphorus is a chemical element with the symbol P and atomic number 15 in its most stable form. However, in this question, we are discussing a radioactive form of phosphorus. The atomic number refers to the number of protons in the nucleus of an atom. For the radioactive form referred to in this question, it is likely that this refers to the isotope phosphorus-32 (P-32), which has an atomic mass of approximately 32.
Let’s clarify the other options:
- B: an atomic mass of 15 is incorrect because that refers to the stable isotope of phosphorus.
- C: an atomic mass of 47 is also incorrect as it does not correspond to any naturally occurring or standard radioactive isotope of phosphorus.
- D: 32 electrons is incorrect, as the number of electrons in a neutral atom is equal to the atomic number, which is 15 for phosphorus.
- E: 17 neutrons is incorrect since phosphorus-32 has 17 neutrons (32 – 15 = 17); however, this does not serve as a correct property under the context of the question that asks for atomic identification.
Thus, the key takeaway is that the radioactive form mentioned in the question corresponds to phosphorus-32, emphasizing the atomic number of 32 and its composition of neutrons and protons.