Which of the following does not belong to the first transition series?

The correct answer is Option (4) → Ag

A transition series is the row of d-block elements in which one d subshell is being filled. The first transition series (3d series) runs from scandium (Z = 21) to zinc (Z = 30): Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn.

• Option (1) Ni — In the first transition series. Ni (Z = 28) is [Ar]3d⁸4s²; its 3d subshell is being filled.

• Option (2) Zn — In the first transition series. Zn (Z = 30) is [Ar]3d¹⁰4s²; it is the last element of the 3d series.

• Option (3) Cr — In the first transition series. Cr (Z = 24) is [Ar]3d⁵4s¹, a 3d element.

• Option (4) Ag — Not in the first transition series. Ag (Z = 47) is [Kr]4d¹⁰5s¹. It fills the 4d orbitals, so it belongs to the second transition series (Y to Cd).

NCERT (2026-27 edition):
The d- and f-Block Elements – …