Carbon has four valence electrons. These electrons are associated for a specific atom and is responsible for forming a bond to different atoms. For carbon, in order to agree with the octet rule, it should have 4 more electrons. For an oxygen atom, there are 6 valence electrons present so it would need two more electrons. Thus, carbon atoms would share electrons with another two oxygen atoms wherein each oxygen atom would form double bonds with the carbon atom. So, the characteristics of these bonds would be that all of the four valence electrons of the carbon are being shared.
