Q58 P - Chemistry: Molecular Nature Of Matter And Change

Question

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

Step-by-Step Solution

Answer

$\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_4{\left({\mathrm{NO}}_2\right)}_2\right]Cl$ - Coordination number: 6; charge: +3

$\left[\mathrm{Cr}{\left({\mathrm{NH}}_3\right)}_6\right]\left[\mathrm{Cr}{\left(\mathrm{CN}\right)}_6\right]$ - Coordination numbers: 6; charges: zero and +6

$K_2\left[{\mathrm{CuCl}}_4\right]$ Coordination number: 4; charge: +2

Step 1: Definition of Coordination Compound

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.

Step 2: Solve the given statements

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.