Which of the following pairs constitute isotones ?

Options

A. `6overset13C` and
`7overset14N`
B. `6overset13C` and
`6overset14C`
C. `7overset14N` and `9overset19F`
D. `7overset14N` and `7overset15N`

Explanation

To determine which pairs constitute isotones, we need to understand the definition of isotones. Isotones are nuclides that have the same number of neutrons but different numbers of protons (atomic numbers).

### Step-by-Step Solution:

1. **Identify the pairs given in the question.**
- The pairs mentioned are:
- (6C13 and 7N14)
- (6C13 and 6C14)
- (14N and 9F19)
- (7N14 and 7N15)

2. **Calculate the number of neutrons for each nuclide.**
- The number of neutrons (N) can be calculated using the formula:
\[ N = A - Z \]
where A is the mass number and Z is the atomic number.

3. **Calculate for the first pair (6C13 and 7N14):**
- For 6C13:
- A = 13, Z = 6
- N = 13 - 6 = 7
- For 7N14:
- A = 14, Z = 7
- N = 14 - 7 = 7
- Both have 7 neutrons, so this pair constitutes isotones.

4. **Calculate for the second pair (6C13 and 6C14):**
- For 6C13:
- N = 13 - 6 = 7
- For 6C14:
- A = 14, Z = 6
- N = 14 - 6 = 8
- They have different numbers of neutrons (7 and 8), so this pair does not constitute isotones.

5. **Calculate for the third pair (14N and 9F19):**
- For 14N:
- A = 14, Z = 7
- N = 14 - 7 = 7
- For 9F19:
- A = 19, Z = 9
- N = 19 - 9 = 10
- They have different numbers of neutrons (7 and 10), so this pair does not constitute isotones.

6. **Calculate for the fourth pair (7N14 and 7N15):**
- For 7N14:
- A = 14, Z = 7
- N = 14 - 7 = 7
- For 7N15:
- A = 15, Z = 7
- N = 15 - 7 = 8
- They have different numbers of neutrons (7 and 8), so this pair does not constitute isotones.

### Conclusion:
The only pair that constitutes isotones is **(6C13 and 7N14)**, as both have 7 neutrons.