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The atom of iron takes oxygen from carbon atom in the carbonated water, because the carbon atom is electrically negative compared with hydrogen atom. The free carbon bonds to the atom of iron instead of hydrogen atom by ionization tendency.
Here, let us explain the origin of electronegativity about NaCl as follows. The chemical reaction on NaCl breaks out among p-orbit of chlorine and s-orbit of sodium. Here, s-orbit is sphere, and p-orbit is spheroid. The s-orbit of Na atom is invaded by p-orbit of Cl atom. The p-orbit of Cl atom invades into the sphere of Na atom. The value of electronegativity on p-orbit becomes large and that of s-orbit becomes small. So, the valence electrons occupy p-orbit of Cl atom and it and become closed shell structure and the valence electron of Na becomes empty and forms a closed shell structure.
But, it is the model of ionic bond. In fact, the valence electron does not transfer to the Cl atom. The electronic state of compound is different from that of isolated atom. The valence electron in NaCl receives pull force from nucleus Cl more than that of Na.
3.2 Reactions of carbon atom
3.2.a A battery is made in carbonated water by using electrode of iron and carbon
As shown in Fig.16 (a),(b), an electromotive force is generated by the battery that is made of iron electrode and carbon electrode in carbonated water. Here, the iron is the negative pole and as the carbon is positive pole. The electric motive force is given by oxidation of iron. When the atom of iron oxidizes by using the oxygen of carbonated water, the anions are transferred toward the electrode of iron in the carbonated water. So, electrons are transferred to the charcoal electrode from the iron electrode in the circuit of outside. That is, the iron electrode becomes a negative electrode.
（a） at the beginning (0.17mA, 0.3V) (b) after 5hours (0.05mA, 0.1V))
Fig.17 The battery where carbonated water is used for the electrolyte, a charcoal is used for the positive electrode and a steel wool is used for the negative electrode.
The voltage gradually decreace from current=0.17mA to opened voltage=0.1V, shorted current=0.05mA. The reason is a result of the reaction.
3.2.b Movement of ion due to electric field in carbonated water
Hydrogen ion of proton exists a lot in carbonated water, because carbonic acid is weak acid. The proton possesses electric charge and it moves by electric field. But hydroxyl ion (OH)-1 does not move due to the external electric field, because the negative ion of OH-1 is collaborating with hydrogen ion in carbonated water. If electric current is poured by using carbon electrodes, the hydrogen ion of proton transfers to the negative electrode.
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