Question

What is the metal oxidation number in the complex ion, ${{[Zn{{(OH)}_{4}}]}^{2-}}$ ?

Answer 1

Hint : Complex ions are ions that have one or more molecules or ions bonded to a central metal ion. They are an example of a coordination complex. The coordination center is the central ion, and the molecules or ions that are bound to it are known as complexing agents or ligands.

Complete Step By Step Answer:
The oxidation state, also known as the oxidation number, describes the degree of oxidation (electronic loss) of an atom in a chemical compound. The oxidation state, which can be positive, negative, or zero in concept, is the hypothetical charge that an atom would have if all bonds to atoms of different elements were entirely ionic, with no covalent component. This is never entirely accurate for real bonds.
Typically, the anion ${{[Zn{{(OH)}_{4}}]}^{2-}}$ , also known as tetrahydroxozincate, or salts thereof, such as sodium zincate $N{{a}_{2}}Zn{{\left( OH \right)}_{4}}$ , the polymeric anion $[Zn{{\left( OH \right)}_{3}}^{-}]$ and its salts, such as $NaZn{{\left( OH \right)}_{3}}\cdot \text{ }{{H}_{2}}O$ an oxide containing zinc and a less electronegative element, e.g. $N{{a}_{2}}Zn{{O}_{2}}$ .
Zincate may also refer to a commercially available zinc supplement, typically formulated as zinc sulfate, in the health supplement industry.
${{[Zn{{(OH)}_{4}}]}^{2-}}$ is a complex ion in which the oxidation number oxidation no. of hydrogen $+I$ and oxygen $+II$ are standard.
$Z{{n}^{2}}+4H{{O}^{-}}\to {{[Zn{{(OH)}_{4}}]}^{2-}}$ As in any chemical equation, charge and mass are conserved.
The ${{[Zn{{(OH)}_{4}}]}^{2-}}$ species is a complex ion, for which there are many examples.

Note :
For metals that can have multiple oxidation states, the oxidation number is represented by a Roman numeral. After the element name (iron(III)), the oxidation number is enclosed in parentheses. The oxidation states are sometimes written as a superscripted number to the right of the element symbol $(F{{e}^{3}}^{+})$ .