Why does water angled 104.45° ?
Because the O-atom is sp3 hybridized, and the repulsion from non-bonding electron pairs is greater than that from bonding electron pairs.
Gokul - good answer. But it doesn't totally explain the divergence of the 104.45 degree angle from the expected 109.47 degree angle - this explains why (I think):
http://xnet.rrc.mb.ca/rcharney/The water molecule.htm
Jim, the divergence was traditionally explained in terms of a greater delocalization of the lone pairs causing the bond angle to be smaller that the symmetric angle - this is what I stated above. However, the information in your reference suggests there is now good reason to believe that in fact, the 2s orbital is unhybridized and the 105 deg = 90 deg + steric repulsion from H atoms.
Thanks for the link.
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