Number of protons , neutrons and electrons in four species A,B,X and Y are respectively 6,6,6, 7,7,7, 6,8,6 and 9,10,10. How many of them are isobars?

Explanation

To solve the problem of identifying how many of the given species A, B, X, and Y are isobars, we need to follow these steps:

### Step 1: Identify the number of protons, neutrons, and electrons for each species.
- **Species A**: Protons = 6, Neutrons = 6, Electrons = 6
- **Species B**: Protons = 7, Neutrons = 7, Electrons = 7
- **Species X**: Protons = 6, Neutrons = 8, Electrons = 6
- **Species Y**: Protons = 9, Neutrons = 10, Electrons = 9

### Step 2: Calculate the mass number for each species.
The mass number is calculated as the sum of protons and neutrons.
- **Mass number of A**: 6 (protons) + 6 (neutrons) = 12
- **Mass number of B**: 7 (protons) + 7 (neutrons) = 14
- **Mass number of X**: 6 (protons) + 8 (neutrons) = 14
- **Mass number of Y**: 9 (protons) + 10 (neutrons) = 19

### Step 3: Identify isobars.
Isobars are species that have the same mass number but different atomic numbers.
- **A**: Mass number = 12
- **B**: Mass number = 14
- **X**: Mass number = 14
- **Y**: Mass number = 19

### Step 4: Compare the mass numbers.
- B and X both have a mass number of 14.
- A has a mass number of 12, and Y has a mass number of 19.

### Conclusion:
The only pair of isobars among the given species is B and X.

### Final Answer:
**There is 1 pair of isobars (B and X).**

---