Which has a tetrahedral pyramidal molecular geometry?
a. nitrate
b. sulfate
c. chlorate
d. no right answer.

Sulfate = tetrahedral

Explanation:

N°          Geometry                                   Formula

2            linear                                            AX2

3       trigonal-planar                           AX3 or AX2E

4      tetrahedral                         AX4/AX3E/AX2E2

a) Nitrate = NO3-

⇒ AX3

⇒ bond angles = 120°

⇒ Coordination number = 3

⇒ Trigonal planar

b) Sulfate = SO42-

The central  S

-atom has four electron domains. It has no lone pairs, so the electron geometry and the molecular geometry are tetrahedral.

⇒AX4

⇒ bond angles = 190.5°

⇒Coordination number = 4

⇒Tetrahedral

c) Chlorate = ClO3-

In ClO3-, the central atom is a Chlorine.

It has 7 valence electrons.  The three oxygen form a double bond giving three bond pairs. The remaining two electrons make a lone pair. The total of 4 electron pairs shows that the molecule is sp3 hybridised.

The shape of sp3 hybrid molecule is a tetrahedral. But there is a lone pair. So, the geometry is pyramidal.

⇒AX4

⇒ bond angles = 190.5°

⇒Coordination number = 3

⇒pyramidal

Diffference between tetrahedral and pyramidal is that tetrahedral no has a lone pair, and has 4 atoms bonded to the central atom, while pyramidal has 1 lone pair  and 3 atoms bonded to the central atom.

Sulfate has a tetrahedral geometry, which is a pyramidal structure