A radioactive nuclide of atomic number Z emits an alpha particle and the daughter nucleus then emits a beta particle. What is the atomic number of resulting nuclide? A) Z-1
B) Z+1
C) Z-2
D) Z-3

A) Z-1

Explanation:

when a radioactive element of atomic number Z emits an alpha particle, the mass of the new nucleus decreases by 2, i.e the new atomic number of the element = ( Z- 2).

Also, when the daughter nucleus emits a beta particle, the new nucleus increases by 1,  that is the new atomic number of the element = (Z + 1).

Thus, the atomic number of resulting nuclide = Z ( - 2) + ( + 1).

                                                                           = Z - 2 + 1

                                                                           = Z - 1

Therefore, the atomic number of resulting nuclide is Z - 1

vapour or gas assuming atmospheriv pressure