Chapter 21, Problem 1PE

Interpretation Introduction

Interpretation:

The formula of the complex ion formed by silver ${\text{Ag}}^{+}$ and two thiosulfate ions ${\text{S}}_2{\text{O}}_3{}^{2-}$, is to be written. The possibility for the existence of this complex ion in the form of ammonium salt and its formula, is to be determined.

Concept Information:

Complex ions are the ions which are formed by the metal atom at the center and the other nonmetal molecules or ions surrounds it.

Lewis acid-base reaction is the reaction between the lewis acid (loss of pair of electrons) and lewis base (gain of pair of electrons).

Ligands are the molecules or ions that bond with a coordinate covalent bond to form a metal ion.

To write the formula for a complex, following rules are utilized:

The symbol for the metal ion is always given first, followed by the ligands.

When more than one kind of ligand is present, anionic ligands are written first (in alphabetical order), followed by neutral ligands (also in alphabetical order).

The charge on the complex is the algebraic sum of the charge on the metal ion and the charges on the ligands.

The formula is placed inside of the square brackets with the charge of the complex ion as a superscript outside the brackets. When the charge is zero the brackets and charge are omitted.

Answer to Problem 1PE

Solution:

The formula of the complex ion that is formed by silver ${\text{Ag}}^{+}$ and two thiosulfate ions ${\text{S}}_2{\text{O}}_3{}^{2-}$ is ${\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]}^{3-}$ and the formula of the ammonium salt formed with comolex ion ${\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]}^{3-}$ is ${\left({\text{NH}}_4\right)}_{\text{3}}\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]$.

Explanation of Solution

The most common oxidation state of silver $\text{Ag}$ is $+1$ is when it loses one electron and becomes ${\text{Ag}}^{+}$ ion. The thiosulfate ions ${\text{S}}_2{\text{O}}_3{}^{2-}$ are the anionic ligands that carry $2-$ charge. Two ${\text{S}}_2{\text{O}}_3{}^{2-}$ ions contributes the total charge of $4-$ and one ${\text{Ag}}^{+}$ ion contributes a charge $1+$, so the net charge of the complex ion is $3-$. Hence, the formula of the complex ion according to the rule of nomenclature for the complex ion is ${\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]}^{3-}$ ion.

The complex ion ${\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]}^{3-}$ is an anion, and the ammonium ion carries $1+$ charge to form a neutral salt where three ammonium ions are required. The formula of the salt is ${\left({\text{NH}}_4\right)}_{\text{3}}\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]$.

Conclusion

According to the rule of nomenclature for the coordination complex, the given complex ions are formulated as ${\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]}^{3-}$. Also, the given complex ion can exist as an ammonium salt with the complex ion and its formula as ${\left({\text{NH}}_4\right)}_{\text{3}}\left[\text{Ag}{\left({\text{S}}_2{\text{O}}_3\right)}_2\right]$.