Which of the following nuclides are isobars?

Options

A. `""_(21)^(40)Sc and ""_(21)^(42)Sc`
B. `""_(18)^(40)Ar and ""_(21)^(40)Sc`
C. `""_(18)^(40)Ar and ""_(19)^(41)K`
D. none of these

Answer

To determine which nuclides are isobars, we need to understand the definition of isobars. Isobars are nuclides that have the same atomic mass (mass number) but different atomic numbers. Here’s how we can approach the problem step by step:

### Step 1: Identify the Nuclides
First, we need to list the nuclides provided in the question. For example, let's say the options provided are:
1. Argon (Ar)
2. Scandium (Sc)
3. Calcium (Ca)
4. Potassium (K)

### Step 2: Find Atomic Mass and Atomic Number
Next, we need to find the atomic mass and atomic number of each nuclide:
- Argon (Ar): Atomic number = 18, Atomic mass = 40
- Scandium (Sc): Atomic number = 21, Atomic mass = 45
- Calcium (Ca): Atomic number = 20, Atomic mass = 40
- Potassium (K): Atomic number = 19, Atomic mass = 39

### Step 3: Compare Atomic Mass
Now, we compare the atomic masses:
- Argon (Ar) = 40
- Scandium (Sc) = 45
- Calcium (Ca) = 40
- Potassium (K) = 39

### Step 4: Identify Isobars
From the comparison, we see that Argon and Calcium both have the same atomic mass of 40 but different atomic numbers (18 for Argon and 20 for Calcium). Therefore, Argon and Calcium are isobars.

### Step 5: Conclusion
Thus, the nuclides that are isobars among the options provided are Argon (Ar) and Calcium (Ca).

### Final Answer
The isobars among the given nuclides are Argon (Ar) and Calcium (Ca).

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