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Is H2O magnetic?

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mapa
#1
May28-10, 12:36 PM
P: 29
I understand that H2O is polarized. The way I see it there is a north pole and a sole pole. If this is correct, why does it not attract magnets?
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Mu naught
#2
May28-10, 01:04 PM
P: 212
Water does in fact interact with magnetic fields, but you need a very strong field! Check out this video.

http://www.youtube.com/watch?v=VB55R...layer_embedded
mapa
#3
May28-10, 01:39 PM
P: 29
Thanks for the help.

solidspin
#4
May28-10, 02:40 PM
P: 10
Is H2O magnetic?

H2O is really not truly magnetic. When you say "magnetic" you probably mean "ferromagnetic" or that it has a permanent magnetic moment. Water can't, because there's no "spot" where unpaired electrons could permanently "live".

Water is paramagnetic, which means that it has a slight magnetic moment, because the last two electrons in oxygen's shell are unpaired and each one is in the p_x* and p_y* orbitals. You can measure this in something called a "gouy balance" - same thing w/ O2 gas or O2 liquid. There's a ton of switching around of these electrons (note the "*", meaning they are in special "antibonding" orbitals), so that's why you only get a very mild, impermanent magnetic moment.

Water has a "big" electric dipole moment, however, b/z oxygen is so electronegative, that the bulk of the time the electrons that came along with, and are covalently shared by, the two hydrogens, spend their time around oxygen.

In solids, where lots of unpaired electrons can permanently live in the crystalline unit cells of compounds like cobalt-iron-neodymium or what have you, can and do have very large permanent magnetic moments...all the unpaired electrons EACH occupy a d-orbital...since they're all pointing in one direction (due to Hund's rules and the Aufbau principle), there's your permanent magnetic moment and, hence, ferromagnetism. Does that help?
alxm
#5
May28-10, 08:31 PM
Sci Advisor
P: 1,866
Quote Quote by solidspin View Post
Water is paramagnetic, which means that it has a slight magnetic moment, because the last two electrons in oxygen's shell are unpaired and each one is in the p_x* and p_y* orbitals.
I'm afraid you've confused water with O2 and atomic orbitals with molecular ones.
Water has no unpaired electrons and is thus diamagnetic. Which, (for the benefit of the original poster), means it's even less magnetic than that - about as un-magnetic as a substance can get.

It's O2 that has two unpaired electrons (in the [tex]\pi^*_x[/tex] and [tex]\pi^*_y[/tex] molecular orbitals), and is thus paramagnetic.


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