What is the EAN of Pt in potassium hexachloroplatinate(IV)?

The correct answer is option 2. 86.

Let us recalculate the Effective Atomic Number (EAN) for potassium hexachloroplatinate(IV) \((K_2[PtCl_6])\):

Given:

Atomic number of platinum (Pt) = \(78\)

Oxidation state of Pt = \(+IV\)

Number of electrons gained by Pt from ligands through coordination = \(2 \times 6 = 12\) (each chloride ligand donates 2 electrons)

Using the formula for EAN:

\(\text{EAN} = (\text{Atomic number of Pt}) - (\text{Oxidation state of Pt}) + (\text{No. of electrons gained by the metal from ligands through coordination}) \)

\(\text{EAN} = (78) - (4) + (12) = 86 \)

So, the Effective Atomic Number (EAN) of Pt in potassium hexachloroplatinate(IV) is indeed \(86\).