Textbook problem 9C.9

[Shannon Moore 2L]

I am just confused in general about this problem and don't really understand the answers. Any help is appreciated!

(a) [NiCl4]2−

(b) [Ag(NH3)2]+

(c) [PtCl2(en)2]2+

(d) [Cr(edta)]−

Answers:

a) 4
b) 2
c) 6
d) 6

[Shannon Moore 2L]

Sorry the question asks what the coordination numbers are of the metal ions in the complexes!

[Joey_Okumura_1E]

The coordination number is the number of points at which a ligand is attached to the central atom. You need to consider the amount of ligands and the denticity of the ligands. For example, in [NiCl4]2−, four Cl ligands are attached to central atom Ni. Cl is monodentate (which means Cl only binds to Ni at one point) so the coordination number is 4. For [PtCl2(en)2]2+, two Cl ligands and two en ligands are attached to central atom Pt. However, because en is bidentate, the coordination number is 6.

[Katherine_Douglas_1F]

Similar to what Joey said, you just have to count the number of points that the ligands are attached to the central atom. [Ag(NH3)2]+ is one silver molecule attached to two ammonia molecules. Since ammonia is a monodentate ligand, the coordination number is 2. [Cr(edta)]- is a bit of a more special case because edta is hexadentate which means that it attaches to the central Chromium atom at six points, making the coordination number of Chromium 6.

[Mina Tadros 3L]

Coordination numbers are the number of ligands that are attached to the central metal cation. These are only for the ligands within the coordination sphere. Since [NiCl4] has 4 ligands attached to the central metal cation, then it has a coordination number of 4. [Ag(NH3)2] has two, thus, it has a coordination number of 2. The rest are solved in the same manner.