Oxidized Having lost electrons

In both of these examples, the metal has been "oxidized" - has lost electrons and increased in oxidation number — while the carbon atoms have gained electrons and been "reduced."... 

Once you have a firm grasp on the rules for oxidation numbers and solving problems involving oxidation numbers, you can use oxidation numbers to determine the substance that undergoes a reduction and an oxidation in a redox reaction. You can tell that a substance has been reduced if it has gained electrons (electrons are a reactant). A substance that has been oxidized has lost electrons (electrons are a product). After the substances that have changed oxidation states in a redox reaction are identified, you then write separate half reactions. Half reactions are two separate reactions that show the oxidation and reduction reactions separately. An example follows. 

A simple but important example is the reaction that occurs if you drop a piece of zinc into a solution of copper sulfate. You will find that the zinc becomes coated in a layer of copper and that some of the zinc dissolves (as ions). You can conclude that the zinc atoms, Zn, in the lump, having lost electrons, have been oxidized to Zn ions. Moreover, because the Cu ions in the solution have been converted to copper atoms, Cu, by gaining electrons, the ions have been reduced (Figure 5.3). This redox reaction might seem rather dull and a waste of zinc, but you will see in Reaction 7 that it is the foundation of the emergence of modem communication systems. 

We recognize redox reactions by noting whether electrons have migrated from one species to another. The loss or gain of electrons is easy to identify for monatomic ions, because we can monitor the charges of the species. Thus, when Br ions are converted into bromine atoms (which go on to form Br2 molecules), we know that each Br ion must have lost an electron and hence that it has been oxidized. When 02 forms oxide ions, 02-, we know that each oxygen atom must have gained two electrons and therefore that it has been reduced. The difficulty arises when the transfer of electrons is accompanied by the transfer of atoms. For example, is chlorine gas, Cl2, oxidized or reduced when it is converted into hypochlorite ions, CIO" ... 

The stoichiometry of transition metal oxides is more variable. Iron, for example, forms three binary oxides. In FeO the iron atoms have lost two electrons each (Fe, O ), and in Fc2 O3 they have lost three electrons each... 

As fuel molecules are oxidized, the electrons they have lost are used to make NADH and FADH2. The function of the electron transport chain and oxidative phosphorylation is to take electrons from these molecules and transfer them to oxygen, making ATP in the process. 

Phenothiazine derivatives and compounds with two or three thiazine rings conjugated to each other, such as 98 and 99 <2004JA1388>, 159, 160, and 161 <2003EJO3534>, have interesting electronic properties (see also Section 12.2) and their cyclic voltammetry has been studied. These compounds are oxidized stepwise until each phenothiazine moiety has lost an electron. 

Widrig et al. [196] have studied voltam-metrically, the SAMs of several -alkanethiols formed on pc-Ag electrodes. Analysis of data showed that during adsorption, the hydrogen of thiol group is lost and the sulfur is oxidized by one electron. Based on the charge required for the reductive desorption of the mono-layer, the surface coverage was found to be 7.0 X 10-10 j -2... 

This work has been criticized rather severely by saying that we are just dumping electrons into the reaction, and there had been a lot of pressure on us to make sodium oxide and see if it really gives the same answer. I do think it would be a very nice thing to have done, but I really don t want to do it. I have lost my enthusiasm for that portion of the problem. 

Type B oxides have a metal excess which is incorporated into the lattice in interstitial positions. This is shown in (b)(1) as an interstitial atom, but it is more likely that the situation in (b)(ii) will hold, where the interstitial atom has ionised and the two electrons so released are now associated with two neighbouring ions, reducing them from to M. Cadmium oxide, CdO, has this type of structure. Oxygen is lost when zinc(II) oxide is heated, forming Zn +JD, oxide vacancies form and to compensate, Zn ions migrate to interstitial positions and are reduced to Zn ions or Zn atoms. Electron transfer can take place between the Zn and ZnTZn resulting in the yellow coloration seen when ZnO is heated. 

These terms are frequently used and may lead to confusion, if used in the wrong context. As a reminder, the valency of an atom is strictly the number of bonds (including o, n and 8) in which it participates in any particular compound. In IF , the iodine atom participates in seven a bonds to the fluorine atoms. The fluorine atoms are individually monovalent. Oxidation states are more useful than valency in describing ionic compounds. In the crystalline solid CaF0, the calcium is best thought of as composed of calcium dications and fluoride anions, Ca2+(F ),. The calcium is in its +2 oxidation state, having lost its valency electrons, and the fluorine atoms are in the -1 oxidation state, both having accepted an elec-... 

Step 6 At this point, you need to remember what we said about oxidation and reduction. One substance is oxidized and the other reduced. As the equations exist right now, the chloride ions have lost 2 electrons, but the chromium atoms have gained 6 electrons. That s impossible The 6 electrons had to come from the chloride ions. In step 6, therefore, we need to equalize the number of electrons in each half-reaction. We need to increase the total number of electrons lost by the chloride ions to 6. To do this, we have to multiply the entire half-reaction by 3 ... 

In oxides, the division between core and valence states should be carried out with care. For example, in strongly ionic materials the cation may have lost all valence electrons to the anion and so the cation/anion interaction involves orbitals on the cation that are atomic core states. In this situation, expHcit inclusion of the outermost cation orbitals would be required for accurate results. Even so, the replacement of the core region with a smoother potential can reduce the calculation time even for H atoms, and so pseudopotentials are available even in this case. 

Oxidation and reduction must always occur together because the reduction process requires a supply of electrons available only from the oxidahon process. At the same time, the oxidation process must have a receiver for lost electrons. 

Oxidation and Reduction Occur Simultaneously We have already studied the electronic concept of oxidation and reduction. If some substance loses electrons (i.e. undergoes oxidation) then the electrons lost by it must be accepted by some other sabstance. The substance that accepts electrons undergoes reduction. Hence it is clear that oxidation and reduction occur simultaneously. For example in the reaction. 

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