Question

Structure of nuclei of three atoms X, Y and Z are as follows
1) X has 90 Protons and 146 Neutrons
2) Y has 92 Protons and 146 Neutrons
3) Z has 90 Protons and 148 Neutrons
Which of the following statements is correct based on above data?

• A. X and Z are isotopes; Y and Z are isobars
• B. X and Y are isotops; X and Z are isobars.
• C. Y and Z are isobars; X and Y are isotopes
• D. X and Z are isotopes; X and Y are isobars

Answer 1

The correct option is A X and Z are isotopes; Y and Z are isobars

Isotopes have same number of protons but different number of neutrons.
X and Z have 90 protons but 146 and 148 neutrons respectively.
Thus, X and Z are isotopes.
Isobars have same mass number but different atomic number.
Y has 92 Protons and 146 Neutrons . Its mass number is $92+146=238$. Its atomic number is 92.
Z has 90 Protons and 148 Neutrons. Its mass number is $90+148=238$. Its atomic number is 90.
Thus, Y and Z are isobars.