What are the charge and coordination number of the central metal ion(s) in each compound of Problem 23.56?

A coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents.

The coordination number is the number of ligands directly attached to central metal ion in a coordination compound. These ligands can be ions, atoms or molecules. The most common coordination number is 0, but it is also not rare to see 2 and 4 as coordination numbers.

$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\left({\mathrm{NO}}_2\right)}_2\right]Cl$ - There are six ligands (4NH₃ and 2NO₂) and bonded with central metal ion, so the coordination number is 6. NH₃ Is neutral, but NO₂ has -1 charge and CI is counter ion with also -1 charge, so the charge of the central metal ion will be +3

$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]\left[\mathrm{Cr}{\left(\mathrm{CN}\right)}_6\right]$ - Both central metal ions have coordination number 6 because there are six ligands (NH₃ and CN bonded with each metal ion. NH₃ is neutral and the first Cr has +3 charge and the one bonded with CN has also +3 charge because CN has -1 charge.

$K_2\left[{\mathrm{CuCl}}_4\right]$- We can see that there are four ligands (Cl) bonded with Cu, so the coordination number of the central metal ion is 4. CI has -1 charge and K is a counter ion with +1 charge, so the charge of the central metal ion will be +2.