Question

question 4
the atomic number of phosphorus (p) is 15. compared with ³¹p, the radioactive isotope ³²p has ______.
one more electron.
one more neutron.
one more proton.
a different atomic number

Explanation:

Isotopes of an element have the same atomic number (same number of protons) but different mass - numbers due to different numbers of neutrons. Phosphorus - 31 ($^{31}P$) and phosphorus - 32 ($^{32}P$) are isotopes. The mass number is the sum of protons and neutrons. Since the atomic number (number of protons) is the same for both ($Z = 15$), and the mass number of $^{31}P$ is 31 and of $^{32}P$ is 32, $^{32}P$ has one more neutron than $^{31}P$.

Answer:

B. one more neutron