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  1. Problems
  2. /Find the oxidation state of the metal in each complex…
MediumChemistryHigh School (11–12)Coordination Compounds › Werner's Theory, Ligands and NomenclatureNumerical

Find the oxidation state of the metal in each complex…

StemPy LabContributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Find the oxidation state of the metal in each complex. Take water, ammonia and carbon monoxide as neutral and chloride and cyanide as −1-1−1.

  • [Mn(H2O)6]2+[\text{Mn}(\text{H}_{2}\text{O})_{6}]^{2+}[Mn(H2​O)6​]2+
  • [CrCl2(H2O)4]+[\text{CrCl}_{2}(\text{H}_{2}\text{O})_{4}]^{+}[CrCl2​(H2​O)4​]+
  • [Ni(CN)4]2−[\text{Ni}(\text{CN})_{4}]^{2-}[Ni(CN)4​]2−
  • [PtCl4(NH3)2][\text{PtCl}_{4}(\text{NH}_{3})_{2}][PtCl4​(NH3​)2​]
  • [Cr(CO)6][\text{Cr}(\text{CO})_{6}][Cr(CO)6​]

Check your answer

Work it out on paper, then type your number. The answer itself stays hidden.

Need a reminder? The key ideaShowHide

The coordination number is the number of donor atoms bonded to the metal, not the number of ligands. The charge on a complex is x+(sum of the ligand charges)x + (\text{sum of the ligand charges})x+(sum of the ligand charges), where xxx is the oxidation state of the metal. A ligand with two or more donor atoms is chelating, and EDTA has six.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

Step 1. Manganese. Water is neutral, so x+0=+2x + 0 = +2x+0=+2 and x=2x = 2x=2.

Step 2. Chromium with chloride. x+2(−1)+0=+1x + 2(-1) + 0 = +1x+2(−1)+0=+1, so x=+3x = +3x=+3.

Step 3. Nickel. x+4(−1)=−2x + 4(-1) = -2x+4(−1)=−2, so x=+2x = +2x=+2.

Step 4. Platinum. The complex is neutral: x+4(−1)+0=0x + 4(-1) + 0 = 0x+4(−1)+0=0, so x=+4x = +4x=+4.

Step 5. Chromium carbonyl. Every ligand is neutral and the complex is neutral, so x=0x = 0x=0.

Answer: +2+2+2, +3+3+3, +2+2+2, +4+4+4 and 000.

Check. Each sum of xxx and the ligand charges gives the charge on the complex.

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  1. Ligands and coordination numberWerner's Theory and Naming Complexes

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