From: Andrew Lorimer Date: Sun, 3 Mar 2019 08:16:44 +0000 (+1100) Subject: start electrochemistry notes X-Git-Tag: yr12~231 X-Git-Url: https://git.lorimer.id.au/notes.git/diff_plain/146c682596915cb38d0caa97ec80e0dd97cc7c86 start electrochemistry notes --- diff --git a/chem/electrochemistry.md b/chem/electrochemistry.md new file mode 100644 index 0000000..2d465e2 --- /dev/null +++ b/chem/electrochemistry.md @@ -0,0 +1,46 @@ +--- +header-includes: +- \usepackage[version=4]{mhchem} +--- + +# Electrochemistry + +## Oxidation states + +Indicates charge (ionisation) of an element + +**Oxidation** - loss of e- +**Reduction** - gain of e- + +Main group elements (i.e. group 2) - generally one oxidation state: + +| elements | valence config | oxidation state | +| ------------- | -------------- | --------------- | +| alkali metals | $s^1$ | +1 | +| alkali earths | $s^2$ | +2 | +| aluminium | $s^2 p^1$ | +2 | +| nitrogen | $s^2 p^3$ | -3 | +| oxygen | $s^2 p^4$ | -2 | +| halogens | $s^2 p^5$ | -1 | +| noble gases | $s^2,\>s^2p^5$ | n/a | + +Transition metals (d shell) may have several oxidation states. + +$$\ce{H_2}$$ + +Common oxidation numbers: + +| elements | common ox. no. in compounds | exceptions | +| ----------------- | --------------------------- | ------------------- | +| main group metals | valency | no | +| hydrogen | +1 | metal hydrides (-1) | +| oxygen | -2 | + + +### Rules for oxidation states + +- oxidation states >3 may only exist in compounds +- oxidation number of free element is 0 +- oxidation number of simple ion is the charge of the ion +- sum of oxidation numbers in polyatomic ion is the charge of the ion +- sum of oxidation numbers of a neutral compound is zero