Which among the following is wrong about isodiaphers?

Options

A. They have the same difference between neutrons and protons or same isotopic number
B. Nuclide and its decay product after -emission are isodiaphers
C. For the reaction `A_m to _(z-2) B^(m-4)+_2He^4,'A'` and 'B' are isodiaphers
D. All are correct

Answer

To solve the question regarding isodiaphers, let's break down the concept step by step:

### Step 1: Understand the Definition of Isodiaphers
Isodiaphers are defined as pairs of nuclides that have the same difference between the number of neutrons and protons. This means that if you take two nuclides, their neutron count (N) and proton count (Z) will satisfy the condition:
\[ N - Z = \text{constant} \]

### Step 2: Analyze the Statements
The question asks which statement about isodiaphers is incorrect. We need to evaluate each statement provided in the options.

1. **Statement 1**: They have the same difference between neutrons and protons.
- This is true by the definition of isodiaphers.

2. **Statement 2**: A nuclide and its decay product after emission are isodiaphers.
- This is also true. For example, if a nuclide undergoes alpha decay, the resulting nuclide will have a specific relationship in neutron and proton counts that can still satisfy the isodiaphers condition.

3. **Statement 3**: They have the same isotopic number.
- This statement is misleading. Isodiaphers do not necessarily have the same isotopic number, as isotopic numbers refer to the total number of nucleons (protons + neutrons), which can vary.

### Step 3: Conclusion
After evaluating the statements, we can conclude that the statement regarding having the same isotopic number is incorrect. Therefore, the answer to the question is the statement that claims they have the same isotopic number.

### Final Answer
The incorrect statement about isodiaphers is that they have the same isotopic number.

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