PREVIOUSLY ASKED IN:
WBPSC Miscellaneous Preliminary 2019
Answer
Na+ and Zn2+
Explanation
A transition metal is defined as an element whose atom or stable ion has an incompletely filled d-subshell. Sodium (Na) is an s-block alkali metal, so Na+ is definitively not a transition metal ion. Zinc (Zn) has an electronic configuration of [Ar] 3d10 4s2. When it forms the Zn2+ ion, it loses the 4s electrons, leaving a completely filled 3d10 subshell. Because its d-subshell is fully filled, Zn2+ does not exhibit typical transition metal properties (like colored ions or variable oxidation states) and is not considered a transition metal ion. Iron (Fe2+) and Cobalt (Co3+) have partially filled d-orbitals, making them true transition metal ions.
Key Points
- > Transition elements are generally found in Groups 3 through 11 of the periodic table.
- > Group 12 elements (Zinc, Cadmium, Mercury) are d-block elements but are not considered transition metals because they have full d-subshells (d10).
- > Sodium (Na) is a highly reactive Group 1 alkali metal belonging to the s-block.
- > Transition metals characteristically form colored compounds, act as catalysts, and show variable oxidation states.
- > Zn2+ salts are white/colorless because the fully filled 3d subshell prevents d-d electron transitions.
Additional Information
Electronic Configuration & Element Types
| Ion | Atomic Number | Outer Configuration | Nature |
|---|---|---|---|
| Na+ | 11 | [Ne] 3s0 | Alkali Metal (s-block) |
| Fe2+ | 26 | [Ar] 3d6 | Transition Metal (d-block) |
| Co3+ | 27 | [Ar] 3d6 | Transition Metal (d-block) |
| Zn2+ | 30 | [Ar] 3d10 | d-block, but NOT transition |
Memory Tips
- Exceptions in d-block: Zinc (Zn), Cadmium (Cd), and Mercury (Hg) sit at the end of the d-block series. Because their d-orbitals are completely full (d10), they are officially excluded from the 'transition metal' family.