Calculate the number of electrons, protons and neutrons in the following species:
`(i) `_(15)^(31)P (ii) `_(15)^(31)P^(3-)`

Answer

To solve the problem, we need to find the number of protons, neutrons, and electrons in the given species. Let's break it down step by step.

### (i) For the species \(_{15}^{31}P\):

1. **Identify the Atomic Number (Z)**:
- The atomic number is given as 15. This represents the number of protons in the atom.
- **Number of Protons = 15**

2. **Identify the Mass Number (A)**:
- The mass number is given as 31. This represents the total number of protons and neutrons in the atom.
- **Mass Number (A) = 31**

3. **Calculate the Number of Neutrons**:
- The number of neutrons can be calculated using the formula:
\[ \text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons} \]
- Substituting the values:
\[ \text{Number of Neutrons} = 31 - 15 = 16 \]

4. **Determine the Number of Electrons**:
- Since the species is neutral, the number of electrons is equal to the number of protons.
- **Number of Electrons = 15**

### Summary for (i):
- **Protons = 15**
- **Neutrons = 16**
- **Electrons = 15**

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### (ii) For the species \(_{15}^{31}P^{3-}\):

1. **Identify the Atomic Number (Z)**:
- The atomic number is still 15, indicating the number of protons.
- **Number of Protons = 15**

2. **Identify the Mass Number (A)**:
- The mass number remains 31.
- **Mass Number (A) = 31**

3. **Calculate the Number of Neutrons**:
- Using the same formula as before:
\[ \text{Number of Neutrons} = \text{Mass Number} - \text{Number of Protons} \]
- Substituting the values:
\[ \text{Number of Neutrons} = 31 - 15 = 16 \]

4. **Determine the Number of Electrons**:
- The species has a charge of -3, indicating that it has gained 3 additional electrons.
- Therefore, the number of electrons is:
\[ \text{Number of Electrons} = \text{Number of Protons} + 3 = 15 + 3 = 18 \]

### Summary for (ii):
- **Protons = 15**
- **Neutrons = 16**
- **Electrons = 18**

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### Final Answers:
- For \(_{15}^{31}P\):
- Protons: 15
- Neutrons: 16
- Electrons: 15

- For \(_{15}^{31}P^{3-}\):
- Protons: 15
- Neutrons: 16
- Electrons: 18

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