An element X decays into element Z by two-step process.
`XrarrY+""_(2)^(4)He`
`YrarrZ+2bare` then

Options

A. X & Z are isobars
B. X & Y are isotopes
C. X & Z are isotones
D. X & Z are isotopes

Answer

D

Explanation

Let A and Z be the mass number and atomic number of X respectively.
`""_(Z)^(A)Xoverset(alpha-"decay")rarr""_(Z-2)^(A-4)Y+""_(2)^(4)He`
`""_(Z-2)^(A-4)Yoverset(beta-"decay")rarr""_(Z)^(A-4)Z+2_(-1)e^(0)`
`therefore XandZ` are isotopes.