VSEPR theory?

Question

H20 forms a tetrahedral shape due to the two lone pairs.Why can't this rule cannot be applied to all molcules with lone pairs?

Answer 1

For VSEPR theory you have to account for the total number of bonds and lone pairs that surround an atom in a molecule.

H2O has an electronic geometry of tetrahedral, its molecular geometry is bent.

In contrast, NH3 has one lone pair it's electronic is also tetrahedral but its molecular geometry is trigonal pyramidal.

CH4 has electronic and molecular tetrahedral geometry

hope this helps.

Answer 2

H2o Vsepr

Answer 3

Actually, one can apply it to all molecules with lone pairs. The trouble is that one doesn't always get the right answer. Like the Lewis theory of the octet rule and the two-electron bond, VSEPR is a simplistic treatment that can break down. A more sophisticated theory is valence bond, in which s-, p-, and d-orbitals hybridize to form new orbitals with different bond angles from the old. So O of H2O hybridizes, while S of H2S does not, resulting in a bond angle of 92deg.

Answer 4

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RE:
VSEPR theory?
H20 forms a tetrahedral shape due to the two lone pairs.Why can't this rule cannot be applied to all molcules with lone pairs?

Answer 5

The electron orbitals form a tetrahedron, the molecule itself is bent All molecules with 4 electron orbitals have a tetrahedral arrangement. Molecules will have different shapes depending on the number of lone pairs and bonding domains. These shapes are all predicted by VSEPR.

Answer 6

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VSEPR Theory is one method that chemists use to predict the shapes of molecules. This theory predicts that electron pairs, whether involved in bonds or as non-bonding pairs, will adopt a geometry in which they maximize the distance from one another in order to minimize repulsions. This will result in a geometry with the lowest possible energy.

Answer 7

I have found a good explanation in wilkipedia. see my link
The basic principle is that the repulsion between lone pairs must be minimal. It works for your case but it depends on the molecule

Answer 8

The answer is D.Electrons will be placed on planar positions as there will be less repulsions than axial positions