The structure of which of the following chloro species can be explained on the basis of dsp$$^2$$ hybridization?

The question asks which chloro species has a structure explained by dsp² hybridization. Dsp² hybridization involves one d orbital, one s orbital, and two p orbitals, resulting in a square planar geometry. This hybridization is typically observed in d⁸ metal ions, especially those from the 4d and 5d series, due to their tendency to form square planar complexes.

Let's analyze each option by determining the oxidation state of the central metal atom and its electron configuration:

Option A: PdCl₄²⁻
The overall charge is -2. Each chloride ion (Cl⁻) has a charge of -1, so four Cl⁻ contribute -4. Let the oxidation state of Pd be $$ x $$. Then:
$$ x + 4 \times (-1) = -2 $$
$$ x - 4 = -2 $$
$$ x = +2 $$
Palladium (Pd) has an atomic number of 46. The electron configuration of Pd in its ground state is [Kr] 4d¹⁰. Removing two electrons for Pd²⁺ gives [Kr] 4d⁸. Pd²⁺ is a d⁸ ion in the 4d series and typically forms square planar complexes using dsp² hybridization.

Option B: FeCl₄²⁻
Overall charge is -2. Oxidation state of Fe ($$ x $$):
$$ x + 4 \times (-1) = -2 $$
$$ x - 4 = -2 $$
$$ x = +2 $$
Iron (Fe) has an atomic number of 26. Fe²⁺ has the configuration [Ar] 3d⁶. Fe²⁺ d⁶ ions usually form tetrahedral or octahedral complexes, not square planar. FeCl₄²⁻ is tetrahedral with sp³ hybridization.

Option C: CoCl₄²⁻
Overall charge is -2. Oxidation state of Co ($$ x $$):
$$ x + 4 \times (-1) = -2 $$
$$ x - 4 = -2 $$
$$ x = +2 $$
Cobalt (Co) has an atomic number of 27. Co²⁺ has the configuration [Ar] 3d⁷. Co²⁺ d⁷ ions typically form tetrahedral or octahedral complexes. CoCl₄²⁻ is tetrahedral with sp³ hybridization.

Option D: NiCl₄²⁻
Overall charge is -2. Oxidation state of Ni ($$ x $$):
$$ x + 4 \times (-1) = -2 $$
$$ x - 4 = -2 $$
$$ x = +2 $$
Nickel (Ni) has an atomic number of 28. Ni²⁺ has the configuration [Ar] 3d⁸. Although Ni²⁺ is d⁸, NiCl₄²⁻ is tetrahedral in solution with sp³ hybridization. It does not adopt a square planar geometry like Pd²⁺ complexes.

Only PdCl₄²⁻, with Pd²⁺ as d⁸ in the 4d series, consistently forms a square planar structure explained by dsp² hybridization. The other ions form tetrahedral complexes.

Hence, the correct answer is Option A.