In this post, we will determine the oxidation numbers in formaldehyde, CH2O.

To determine the oxidation number of an atom(s) in a molecule or an ion, start with the known oxidation numbers and the rules summarized below:



Keep in mind that the summary is zero for neutral molecules and is equal to the charge for ions.

For CH2O, the elements with standard oxidation states are oxygen (-2), and hydrogen (+1) so, we need to determine the oxidation state of the carbon. 

Assign x for the oxidation state of N and set up an equation. 

 1x + 2(+1) + 1(-2) = 0, x = 0


Further Reading


More examples of the oxidation state in this multiple-choice quiz:


Oxidation State and Redox Reactions Quiz


Reactions in Aqueous Solutions Quiz

Leave a Comment