d-Block elements
The d-block of the periodic table contains the elements in which the d orbitals are progressively filled in each of the four long periods. The d-block elements are also known as transition metals. Originally, the name transition metals was derived from the fact their chemical properties were transitional between those of s- and p-block elements. They show numerous oxidation states. All the transition elements exhibit typical metallic properties such as high tensile strength, ductility, malleability, thermal and electrical conductivity. Another important property of transition metals is their catalytic activity. Transition metals generally have high melting and boiling points. Many d-block elements are colored.
Select the pair of d block metals that do not exhibit variable oxidation states:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Sc, Zn
Transition elements show variable oxidation states because the energies of their (n−1)d and ns orbitals are very close. After the ns electrons are lost, one or more d electrons can also be removed, giving several stable oxidation states. An element shows only one oxidation state when losing any other number of electrons does not give a stable arrangement:
Sc (Z = 21, [Ar]3d14s2): loses all three outer electrons to reach the stable argon configuration, so it shows only +3.
Zn (Z = 30, [Ar]3d104s2): loses only the two 4s electrons; the full 3d10 set is not used in bonding, so it shows only +2.
Ti (Z = 22, [Ar]3d24s2): shows +2, +3 and +4.
Cr (Z = 24, [Ar]3d54s1): shows +2, +3 and +6, and also +4 and +5.
Cu (Z = 29, [Ar]3d104s1): shows +1 and +2.
Option (1) Cr, Cu — Both show variable oxidation states. Chromium shows +2 to +6 and copper shows +1 and +2.
Option (2) Sc, Ti — Ti shows variable oxidation states. Titanium shows +2, +3 and +4 (only Sc is fixed at +3).
Option (3) Sc, Zn — Neither shows variable oxidation states. Sc shows only +3 and Zn only +2.
Option (4) Cu, Zn — Cu shows variable oxidation states. Copper shows +1 and +2 (only Zn is fixed at +2).
NCERT (2026-27 edition):
Oxidation States
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| 14-05 S2 11-05 S1 | – | – | – | – |