Carbon is in a progressively more oxidized state from alkanes to alcohol to aldehyde/ketone to carboxylic acid to carbon dioxide. Progressing up the scale involves a continuous transfer of 'electron control' from carbon to oxygen. Because oxygen (3.5 on the Pauling scale) is more electronegative than carbon (2.5), in terms of oxidation-reduction, electrons shared between the two atoms within covalent bonds are said to belong to oxygen. At the aliphatic end of the scale, carbon is bonded to other carbons or hydrogen; at the oxidized end, carbon is bound to oxygen. A carbon in a primary alcohol is in a relatively reduced state, with an oxidation number of -1 (gaining two electrons from bonding with two hydrogens and losing one electron in bonding to oxygen). This carbon will have an oxidation state of +1 upon oxidation to an aldehyde and +3 upon further oxidation to carboxylic acid.