Question

What is the geometry of water molecules?
A) Distorted tetrahedral
B) Tetrahedral
C) Trigonal planar
D) Diagonal

Answer 1

The answer here for this question is based on the basic concept of inorganic chemistry that deals with the VSEPR theory and also from the fact that it does not have the linear structure but is slightly bent due to lone pair repulsion.

Complete answer:
From the lower classes of inorganic chemistry, we have come across the concepts that deal with the prediction of shapes of molecules based on several theories.
- One among those theories is the valence shell electron pair repulsion theory or VSEPR theory. This theory also gives information of bond angles, bond length etc.
Let us now see what this theory states and how we can predict structure.
- In a water molecule, we know that there are two hydrogen atoms attached to one oxygen atom with the oxygen atom being the central atom.
- By the electronic configuration of oxygen atoms we can say that it has 2, 6 valence electrons in its shell.
The two hydrogen atoms contribute one electron each and therefore, the oxygen is left with a total of four electrons which are present as two lone pairs.
- Therefore, for the coordination number 4 that is total of eight electrons or 4 electron pairs the corresponding hybridisation is $s{{p}^{3}}$ and the geometry for this hybridisation is tetrahedral with bond angle ${{109}^{0}}{{5}^{'}}$ but due to lone pair repulsion, it reduces to ${{104}^{0}}5'$. Thus, water has bent structure and therefore is considered as having distorted tetrahedral.

Therefore correct answer is option A).

B<>Note: **There are several drawbacks for the VSEPR theory because it fails to determine the shapes and geometry for isoelectronic molecules and is unable to explain the atomic orbital overlaps and do not confuse VSEPR with VBT as VBT explains the creation of chemical bonds between atoms of molecules whereas VSEPR explains geometry of molecules.