Oxidation state trends in group 4

Examples from tin chemistry
By 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. However, tin(IV) is still the more stable oxidation state of tin.
That means that it will be fairly easy to convert tin(II) compounds into tin(IV) compounds. This is best shown in the fact that Sn²⁺ ions in solution are good reducing agents.
For example, a solution containing tin(II) ions (for example, tin(II) chloride solution) will reduce a solution of iodine to iodide ions. In the process, the tin(II) ions are oxidised to tin(IV) ions.

	Note: For simplicity, I am writing this equation (and the next few) as if the product contained simple tin(IV) ions. In fact, simple tin(IV) ions don't exist in solution. In these examples, they will usually be a part of a much larger complex ion. Don't worry about this at this level.
Tin(II) ions also reduce iron(III) ions to iron(II) ions. For example, tin(II) chloride solution will reduce iron(III) chloride solution to iron(II) chloride solution. In the process, the tin(II) ions are oxidised to the more stable tin(IV) ions. Tin(II) ions will also, of course, be easily oxidised by powerful oxidising agents like acidified potassium manganate(VII) solution (potassium permanganate solution). This reaction could be used as a titration to find the concentration of tin(II) ions in a solution.
	Note: If you aren't happy about titration calculations (including those involving potassium manganate(VII) ), you might be interested in my chemistry calculations book.
And as a final example . . . In organic chemistry, tin and concentrated hydrochloric acid are traditionally used to reduce nitrobenzene to phenylamine (aniline). This reaction involves the tin first being oxidised to tin(II) ions and then further to the preferred tin(IV) ions.
	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. Use the BACK button on your browser to return to this page if you choose to follow this link.