To determine the number of protons, neutrons, and electrons in the ion [tex]\( {}_{15}^{31} P ^{3-} \)[/tex], let's analyze the information provided:
1. Protons:
- The atomic number (Z) of phosphorus (P) is 15. The atomic number is equal to the number of protons in the nucleus.
- Therefore, the number of protons in [tex]\( {}_{15}^{31} P ^{3-} \)[/tex] is 15.
2. Neutrons:
- The mass number (A) of phosphorus in this case is 31. The mass number is the total number of protons and neutrons in the nucleus.
- To find the number of neutrons, we subtract the atomic number from the mass number:
[tex]\[
\text{Number of neutrons} = A - Z = 31 - 15 = 16
\][/tex]
- Therefore, the number of neutrons in [tex]\( {}_{15}^{31} P ^{3-} \)[/tex] is 16.
3. Electrons:
- In a neutral phosphorus atom, the number of electrons would be equal to the atomic number, which is 15.
- However, this ion has a [tex]\(3-\)[/tex] charge, meaning it has gained 3 extra electrons.
- Therefore, the number of electrons is:
[tex]\[
\text{Number of electrons} = 15 + 3 = 18
\][/tex]
- Thus, the number of electrons in [tex]\( {}_{15}^{31} P ^{3-} \)[/tex] is 18.
So, the ion [tex]\( {}_{15}^{31} P ^{3-} \)[/tex] contains:
- 15 protons,
- 16 neutrons,
- 18 electrons.
