Question

What is effective atomic number? Calculate effective atomic number of copper $(\mathrm{Z}=29)$ in ${\left[\mathrm{Cu}({\mathrm{NH}}_3{)}_4\right]}^{2+}$.

Answer 1

Effective atomic number (EAN):

• It is defined as the total number of electrons present around the central metal atom in a complex.
• The formula to calculate the effective atomic number is as follows:

$\mathrm{EAN}=\mathrm{Z}–\mathrm{X}+(2\times \mathrm{Y})$

Where,

• $\mathrm{Z}$ is atomic number
• $\mathrm{X}$ is oxidation number
• $\mathrm{Y}$ is coordination number

Step 1: Given,

• Chemical complex $={\left[\mathrm{Cu}({\mathrm{NH}}_3{)}_4\right]}^{2+}$
• Atomic number of central metal atom $\left(\mathrm{Cu}\right),\mathrm{Z}=29$
• Oxidation number $=+2$
• Coordination number $=4$

Step 2: To determine the effective atomic number by using formula.

$$\begin{gathered} \mathrm{EAN}=\mathrm{Z}–\mathrm{X}+(2\times \mathrm{Y}) \\ \mathrm{EAN}=29–2+(2\times 4) \\ \mathrm{EAN}=29–2+8 \\ \mathrm{EAN}=35 \end{gathered}$$

Therefore, the effective atomic number of copper in ${\left[\mathrm{Cu}({\mathrm{NH}}_3{)}_4\right]}^{\mathbf{2}\mathbf{+}}$ is $\mathbf{35}$.