Write the formula for the complex ion formed by the metal ion Cr3 + and six NO2 - ions as ligands. Decide whether the complex could be isolated as a chloride salt or a potassium salt, and write the formula for the appropriate salt

Answer:The metal complex formed would have the following formula [Cr (NO₂) ₆]³⁻. The complex has a net negative charge and hence it can only be isolated as a salt with a positive cation so the formed complex could be isolated as potassium salt. The formula for salt would be K₃[Cr (NO₂) ₆].

Explanation:

The metal ion given to us is Cr³⁺ (Chromium) in + 3 oxidation state.

The electronic configuration for the metal ion is [Ar]3d³ so there are vacant 3d metal orbitals which are available and hence 6 NO₂⁻ ligands can easily attack the metal center and form a metal complex.

The charge on the overall complex can be calculated using the oxidation states of metal and ligand which is provided.

The (chromium) Cr³⁺ metal has + 3 charge and 6 NO₂⁻ (nitro) ligands have - 6 charge and since the ligands will be providing a total of 6 - (negative) charge and hence only 3 - (negative) charge can be neutralized so a net 3 - negative charge would be present on the overall complex which is basically present at the metal center:

charge on the complex=+3-6=-3

Let X be the Oxidation state of Cr in complex = [Cr (NO₂) ₆]³⁻

X-6=-3

X=-3+6

X=+3

so our calculated oxidation state of Cr is + 3 which matches with the provided in question.

As we can see that the overall metal complex has a net negative charge and hence and only positively charged cations can form a salt with this metal complex and hence only potassium K⁺ ions can form salt with the metal complex.

since overall charge present on the metal complex is - 3 so 3 K⁺ ion would be needed to neutralize it and hence the formula of the metal salt would be K₃[Cr (NO₂) ₆].