The nuclei of which one of the following pairs of nuclei are isotons ?

Options

A. `._34 Se^74 , ._31Ga^71`
B. `._42 Mo^92, ._40Z r^92`
C. `._38 Sr^84, ._38 Sr^86`
D. `._20 Ca^40, ._16 S^32`

Explanation

To determine which pair of nuclei are isotons, we need to understand the definition of isotones. Isotones are nuclei that have the same number of neutrons but different numbers of protons.

### Step-by-Step Solution:

1. **Identify the Nuclei**: First, we need to identify the pairs of nuclei given in the question. Let's assume we have pairs like (A, B), (C, D), etc.

2. **Determine the Atomic Numbers and Mass Numbers**: For each nucleus in the pairs, we need to find their atomic number (Z) and mass number (A). The mass number is the total number of protons and neutrons in the nucleus, while the atomic number is the number of protons.

3. **Calculate the Number of Neutrons**: The number of neutrons (N) in a nucleus can be calculated using the formula:
\[ N = A - Z \]
where A is the mass number and Z is the atomic number.

4. **Compare the Number of Neutrons**: After calculating the number of neutrons for each nucleus in the pairs, we compare them. If two nuclei have the same number of neutrons, they are isotones.

5. **Select the Correct Pair**: From the calculations, select the pair of nuclei that have the same number of neutrons.

### Example Calculation:
- Let's say we have two nuclei:
- Nucleus 1: \( ^{14}_{6}C \) (Carbon)
- Nucleus 2: \( ^{15}_{7}N \) (Nitrogen)

1. For Carbon:
- Mass number (A) = 14
- Atomic number (Z) = 6
- Neutrons (N) = 14 - 6 = 8

2. For Nitrogen:
- Mass number (A) = 15
- Atomic number (Z) = 7
- Neutrons (N) = 15 - 7 = 8

Since both nuclei have 8 neutrons, they are isotones.

### Final Answer:
The pair of nuclei that are isotones will be the one that has the same number of neutrons.