VSEPR theory?

Question

what shape does H2O form?Is it terhedral due to the two lone pairs? This rule cannot be aplied to all molecules.

Answer 1

VSEPR lets you predict the arrangement of "things" (bonds and non-bonding pairs of electrons) around pretty much any central atom. So, in the case of the oxygen in water, there are 4 pairs of electrons around the oxygen atom--2 bonds and 2 non-bonding pairs. So, those 4 "things" will be arranged tetrahedrally. Once you've arrived at that conclusion, the SHAPE of the molecule is determined by looking ONLY at the arrangement of the atoms around the central atom. Since the two bonds from the oxygen to the hydrogens are arranged at two of the points of the tetrahedron, the SHAPE of a water molecule is "bent".

Again, the geometry of the electron pairs is one thing, the shape of the molecule is determined by looking ONLY at the atoms in the molecule.

Hope this helps...