# What is the metal oxidation number in the complex ion, [Zn(OH)_4]^(2-)?

Mar 19, 2016

$Z n {\left(O H\right)}_{4}^{2 -}$ is a complex ion in which the oxidation number of $Z n$ is $+ I I$. Oxidation numbers of hydrogen ($+ I$) and oxygen ($- I I$) are standard.

#### Explanation:

How do we know this? Well, look at its formation reaction:

$Z {n}^{2 +} + 4 H {O}^{-} \rightarrow {\left[Z n {\left(O H\right)}_{4}\right]}^{2 -}$

Charge and mass are conserved, as in every chemical equation. The ${\left[Z n {\left(O H\right)}_{4}\right]}^{2 -}$ species is a complex ion, for which there are many examples.

Mar 19, 2016

Starting with the common grouping of a hydroxyl (OH) as ${O}^{- 2} , {H}^{+ 1}$ for a net charge of -1. That gives a total of -4 charge for the four OH groups. If the whole molecule has a charge of -2, the Zn must be $Z {n}^{+ 2}$. Checking the Periodic Table, this is a highly likely oxidation state (giving up its 4s electrons).