Re: Questions about Highschool chemistry
Posted by Uncle Al on Feb 03, 2004 at 19:49
(68.5.243.16)Re: Questions about Highschool chemistry (RG)
To a first approximation, put the lone pairs as far from each other as possible, then put in the bonds. You have 4 electrons left over or two lone pairs, plus four Xe-F bonds to make six total orbital lobes. A good first guess is an octahedral coordination sphere.
Put Xe at the center of the octahedron. Put the two lone pairs at opposite apices. Now the four fluorines form a square-planar array at the equator, which is correct for XeF4.
XeF6 is a nasty beast. It has a stereoactive lone pair and six fluorines to give a pseudo 7-coordinate structure that is fluxional (constantly rearragnes to give iitelf back with atom positions scrambled.
There are more sophisticated treatments that have better predictive power in nasty and complex cases.
--
Uncle Al
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
(Do something naughty to physics)