Question

What is an effective atomic number? Calculate effective atomic number of copper $ \left( {Z = 29} \right) $ in $ {\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }} $

Answer 1

Hint:Effective atomic number is used to find the stability of the metal in coordination complexes. To solve this question, you must recall the formula for calculating the effective atomic number of a metal.
Formula used: $ {\text{EAN}} = \left( {{\text{Z}} - {\text{O}}{\text{.S}}{\text{.}}} \right) + \left( {{\text{C}}{\text{.N}}{\text{.}} \times {\text{2}}} \right) $
Where, $ {\text{EAN}} $ is the effective atomic number of the central metal atom/ ion
   $ {\text{Z}} $ is the atomic number of the metal whose EAN is to be found
   $ {\text{O}}{\text{.S}}{\text{.}} $ is the oxidation state of the central metal atom/ ion in the complex.
And, $ {\text{C}}{\text{.N}}{\text{.}} $ is the coordination number of the central metal in the complex.

Complete step by step answer:
Effective atomic number or EAN is the total number of electrons present on the central metal atom or ion in a coordination complex including the electrons donated by the ligands. If the EAN of a metal is equal to the number of electrons of a noble gas, the complex is said to be stable.
To find the Effective atomic number of copper, we use the formula,
   $ {\text{EAN}} = \left( {{\text{Z}} - {\text{O}}{\text{.S}}{\text{.}}} \right) + \left( {{\text{C}}{\text{.N}}{\text{.}} \times {\text{2}}} \right) $
Substituting the values, we get,
   $ {\text{EAN}} = \left( {29 - 2} \right) + \left( {2 \times 4} \right) = 27 + 8 $
   $ {\text{EAN}} = 35 $
Thus, the effective atomic number in $ {\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }} $ is $ 35 $

Note:
Coordination compounds are a type of addition compound.
 Coordination compounds are the compounds in which a central metal atom is linked by coordination bond to a number of ligands, which may either be ions or neutral molecules, i.e. by donation of lone pairs by the ligands to the central metal atom. If this compound carries a positive or negative charge, it is called a complex ion. These complex ions are relatively stable and they do not lose their identity in aqueous solution like double salts.
Apart from coordination compounds, the other types of addition compounds are double salts. Unlike coordination compounds, double salts are stable only in crystalline state and lose their identity in solution form.