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In an electrochemical cell, the anode undergoes oxidation and the cathode undergoes reduction. This means that the anode loses electrons while the cathode gains electrons.
However, the anode is negatively-charged while the cathode is positively-charged. Why is this so?
The electrons which are "given up" by the oxidized species at the anode flow from the anode through the electric circuit to the cathode, where they are "needed" for the reduction reaction. The oxidation creates an excess of electrons (negative charge) at the anode, which is compensated by the consumption of electrons at the electron-deficient cathode (positive charge) for the reduction reaction. In summary, the flow of electrons in the electrochemical cell is from anode (electron source) to cathode (electron drain).
Oxidized species give up electrons to an electron pool which prior to their flow to the other half cell create a large negative charge on the electrode where oxidation takes place.
