However, just giving it a name like "inert pair effect" explains nothing. This is often known as the inert pair effect - and is dominant in lead chemistry. The oxidation state of +4 is where all these outer electrons are directly involved in the bonding.Īs you get closer to the bottom of the Group, there is an increasing tendency for the s 2 pair not to be used in the bonding. There's nothing surprising about the normal Group oxidation state of +4.Īll of the elements in the group have the outer electronic structure ns 2np x 1np y 1, where n varies from 2 (for carbon) to 6 (for lead). Trying to explain the trends in oxidation states Once again, the lead is reduced from the +4 to the more stable +2 state. Lead(IV) oxide also reacts with concentrated hydrochloric acid, oxidising some of the chloride ions in the acid to chlorine gas. and lead(IV) oxide decomposes on heating to give lead(II) oxide and oxygen. Lead(IV) chloride, for example, decomposes at room temperature to give lead(II) chloride and chlorine gas: This time, the lead(II) oxidation state is the more stable, and there is a strong tendency for lead(IV) compounds to react to give lead(II) compounds. Use the BACK button on your browser to return to this page if you choose to follow this link. Note: This reaction is dealt with in some detail in the organic chemistry section of the site on a page about the preparation of phenylamine. This reaction involves the tin first being oxidised to tin(II) ions and then further to the preferred tin(IV) ions. In organic chemistry, tin and concentrated hydrochloric acid are traditionally used to reduce nitrobenzene to phenylamine (aniline). Note: If you aren't happy about titration calculations (including those involving potassium manganate(VII) ), you might be interested in my chemistry calculations book. This reaction could be used as a titration to find the concentration of tin(II) ions in a solution. Tin(II) ions will also, of course, be easily oxidised by powerful oxidising agents like acidified potassium manganate(VII) solution (potassium permanganate solution). In the process, the tin(II) ions are oxidised to the more stable tin(IV) ions. For example, tin(II) chloride solution will reduce iron(III) chloride solution to iron(II) chloride solution. Tin(II) ions also reduce iron(III) ions to iron(II) ions. In these examples, they will usually be a part of a much larger complex ion. In fact, simple tin(IV) ions don't exist in solution. Note: For simplicity, I am writing this equation (and the next few) as if the product contained simple tin(IV) ions. In the process, the tin(II) ions are oxidised to tin(IV) ions. This is best shown in the fact that Sn 2+ ions in solution are good reducing agents.įor example, a solution containing tin(II) ions (for example, tin(II) chloride solution) will reduce a solution of iodine to iodide ions. That means that it will be fairly easy to convert tin(II) compounds into tin(IV) compounds. However, tin(IV) is still the more stable oxidation state of tin. Carbon monoxide is a strong reducing agent because it is easily oxidised to carbon dioxide - where the oxidation state is the more thermodynamically stable +4.įor example, carbon monoxide reduces many hot metal oxides to the metal - a reaction which is used, for example, in the extraction of iron in a blast furnace.īy the time you get down the Group as far as tin, the +2 state has become increasingly common, and there is a good range of both tin(II) and tin(IV) compounds. The only common example of the +2 oxidation state in carbon chemistry occurs in carbon monoxide, CO. With tin, the +4 state is still more stable than the +2, but by the time you get to lead, the +2 state is the more stable - and dominates the chemistry of lead. However, as you go down the Group, there are more and more examples where the oxidation state is +2, such as SnCl 2, PbO, and Pb 2+. Because carbon is more electronegative than hydrogen, its oxidation state in this instance is -4! Warning: Don't fall into the trap of quoting CH 4 as an example of carbon with a typical oxidation state of +4. The typical oxidation state shown by elements in Group 4 is +4, found in compounds like CCl 4, SiCl 4 and SnO 2. Some examples of the trends in oxidation states
Use the BACK button on your browser to return quickly to this page. Note: If you aren't happy about oxidation and reduction (including the use of oxidation states), it is essential to follow this link before you go any further. It looks at the increasing tendency of the elements to form compounds in which their oxidation states are +2, particularly with reference to tin and lead.
This page explores the oxidation states (oxidation numbers) shown by the Group 4 elements - carbon (C), silicon (Si), germanium (Ge), tin (Sn) and lead (Pb).
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