Question

which of the following molecules has tetrahedral molecular geometry?
a ammonia
b water
c methane
d all of the above

Explanation:

Step1: Determine molecular geometry of ammonia ($NH_3$)

Using VSEPR theory, $NH_3$ has 3 bonding pairs and 1 lone pair. The electron - pair geometry is tetrahedral. But due to the lone pair, the molecular geometry is trigonal pyramidal (derived from tetrahedral electron - pair geometry).

Step2: Determine molecular geometry of water ($H_2O$)

For $H_2O$, there are 2 bonding pairs and 2 lone pairs. The electron - pair geometry is tetrahedral. The molecular geometry is bent (derived from tetrahedral electron - pair geometry).

Step3: Determine molecular geometry of methane ($CH_4$)

In $CH_4$, there are 4 bonding pairs and no lone pairs. According to VSEPR theory, the molecular geometry is tetrahedral.

Answer:

C. Methane