Question

The four atomic species can be represented as given below. Which of these are isobars?

• A. (1) and (2)
• B. (2) and (4)
• C. (2) and (3)
• D. (1) and (4)

Answer 1

The correct option is C

(2) and (3)

The correct option is (C).

Explanation of correct option:

1. The different atoms which have the same mass number i.e., the sum of the neutrons and protons in the nucleus of each is the same; but have different atomic numbers are called Isobars.
2. Due to different atomic numbers, the isobars will have different atomic structures and therefore, will differ in chemical properties.
3. Atomic number is written on the lower side of the symbol and the mass number is written on the upper side.
4. ${}_{61}{}^{200}\mathrm{X}$ and ${}_{58}{}^{200}\mathrm{X}$ are isobars as they both have the same mass number but their atomic numbers are different.

Explanation of incorrect option:

Option (A): ${}_{60}{}^{201}\mathrm{X}$ and ${}_{61}{}^{200}\mathrm{X}$ are not isobars as they don't have the same mass number.

Option (B): ${}_{61}{}^{200}\mathrm{X}$ and ${}_{60}{}^{203}\mathrm{X}$ also not isobars they also don't have the same mass number.

Option (D): ${}_{60}{}^{201}\mathrm{X}$ and ${}_{60}{}^{203}\mathrm{X}$ are isotopes as they have the same atomic number and different mass numbers.

Thus, The four atomic species can be represented as given below. In which ${}_{61}{}^{200}\mathrm{X}$ and ${}_{58}{}^{200}\mathrm{X}$ are isobars.