For the water molecule, oxygen is electronegative than hydrogen. the difference in electronegativity signifies that the hydrogen-oxygen bond is according to the electronegativity difference between the atoms in water, it would be appropriate to label hydrogen with the symbol, and oxygen with the symbol, based on the electronegativity difference between carbon and oxygen, the bonds in carbon dioxide are according to the electronegativity difference between the atoms in carbon dioxide, it would be appropriate to label oxygen with the symbol, and carbon with the symbol, based on the electronegativity difference between carbon and hydrogen, the bonds in methane are according to the electronegativity difference between the atoms in methane, it would be appropriate to label hydrogen with the symbol, and carbon with the symbol,