1--- 2header-includes: 3- \usepackage[version=4]{mhchem} 4--- 5 6# Electrochemistry 7 8## Oxidation states 9 10Indicates charge (ionisation) of an element 11 12**Oxidation** - loss of e- 13**Reduction** - gain of e- 14 15Main group elements (i.e. group 2) - generally one oxidation state: 16 17| elements | valence config | oxidation state | 18| ------------- | -------------- | --------------- | 19| alkali metals | $s^1$ | +1 | 20| alkali earths | $s^2$ | +2 | 21| aluminium | $s^2 p^1$ | +2 | 22| nitrogen | $s^2 p^3$ | -3 | 23| oxygen | $s^2 p^4$ | -2 | 24| halogens | $s^2 p^5$ | -1 | 25| noble gases | $s^2,\>s^2p^5$ | n/a | 26 27Transition metals (d shell) may have several oxidation states. 28 29$$\ce{H_2}$$ 30 31Common oxidation numbers: 32 33| elements | common ox. no. in compounds | exceptions | 34| ----------------- | --------------------------- | ------------------- | 35| main group metals | valency | no | 36| hydrogen | +1 | metal hydrides (-1) | 37| oxygen | -2 | 38 39 40### Rules for oxidation states 41 42- oxidation states >3 may only exist in compounds 43- oxidation number of free element is 0 44- oxidation number of simple ion is the charge of the ion 45- sum of oxidation numbers in polyatomic ion is the charge of the ion 46- sum of oxidation numbers of a neutral compound is zero