EasyChemistryHigh School (11–12)Coordination Compounds › Werner's Theory, Ligands and NomenclatureNumericalA-LevelBoard ExamIB
Find the coordination number of the metal in each complex…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Find the coordination number of the metal in each complex. In the first the ligand is ammonia. In the second it is ethane-1,2-diamine (en). In the third it is the EDTA ion. In the fourth it is diethylenetriamine (dien), which has three donor atoms.
Need a reminder? The key ideaShow
The coordination number is the number of donor atoms bonded to the metal, not the number of ligands. The charge on a complex is , where 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. The zinc complex. Four ammonia molecules, one donor atom each: .
Step 2. The palladium complex. Two en ligands with two donor atoms each: .
Step 3. The calcium complex. One EDTA ion with six donor atoms: .
Step 4. The cobalt complex. Two dien ligands with three donor atoms each: .
Answer: 4, 4, 6 and 6.
Watch out. The numbers of ligands are 4, 2, 1 and 2. They are not the coordination numbers.
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