Carbon Oxides and stability
Why is $\ce{C2O4}$ unstable?

Have you tried drawing it?

I get four different kinds of structures for it:


$\ce{(O=)O^{.}C-CO^{.}(=O)}$
$\ce{(O^{.})2C-C(O^{.})2}$
$\ce{O#C-O-CO^{.}(=O)}$
$\ce{O#C-O-O-C#O}$


They are unstable for the following reasons:


Biradical
Tetraradical (This won't really exist anywhere near anything else.)
Radical
Peroxo bond, very easy to break homolytically.


All of these compounds can easily decompose to give (the thermodynamical Mariana trench) carbon dioxide:
$$\ce{C2O4 -&gt; 2CO2}$$

That is why it is so unstable.

Reduce 'em!


  And would adding hydrogens to a carbon oxide make the carbon oxide even more stable?


Yes. If you start reducing the compounds above, you will end up with ketones and water (because geminal hydroxy groups tend to give water and ketones), or even alcohols (if you continue reducing).