coordination number

[asannajust_1J]

How do you approach this problem? not sure of my answers... determine the coordination number of the metal ion in each of the following complexes: (a) [NiCl4]2–; (b) [Ag(NH3)2]1 ; (c) [PtCl2(en)2]21 ; (d) [Cr(edta)]2

[Daria Azizad 1K]

I generally approach these problems by first identifying what ligands are in the coordinate sphere, so for (a), the ligand is chlorine. Since we know that Cl has a -1 charge and that there are four of them, that means the charge of nickel plus the charge of the chlorines will equal the charge of the compound. So, that means the charge of nickel will be 6+. For naming them, always start with the ligand and if there are multiple, go alphabetically.

[asannajust_1J]

How does that tell you the coordination number?

[Anisha Chandra 1K]

The coordination number is just the number of bonds formed. So for A, the answer would be 4 bonds because 4 chlorines are bonded to one nickel atom.

[ShravanPatel2B]

the coordination number is found by observing how many ligands are attached to the central atom

[Verity Lai 2K]

The coordination number is just the number of bonds on the central atom so I would draw the lewis structure so you have a visual and can easily identify the coordination number.

[Daniel Toscano 1L]

to add on, be aware of polydentate ligands bonded to the metal as they also contribute to the coordination number. For example, if a metal is only bonded to 1 bidentate ligand than the coordination number would be 2 as the ligand is bonded to the metal 2 times