The number of species from the following that have pyramidal geometry around the central atom is _______. $$S_2O_3^{2-}$$, $$SO_4^{2-}$$, $$SO_3^{2-}$$, $$S_2O_7^{2-}$$

Count species with pyramidal geometry around the central atom from: $$S_2O_3^{2-}$$, $$SO_4^{2-}$$, $$SO_3^{2-}$$, $$S_2O_7^{2-}$$.

$$S_2O_3^{2-}$$ (thiosulphate):

The central sulfur atom is bonded to 3 oxygen atoms and 1 sulfur atom in a tetrahedral arrangement (similar to $$SO_4^{2-}$$). Not pyramidal.

$$SO_4^{2-}$$ (sulphate):

S is surrounded by 4 oxygen atoms. Geometry: tetrahedral. Not pyramidal.

$$SO_3^{2-}$$ (sulphite):

S has 3 bond pairs (to O atoms) + 1 lone pair. Electron geometry is tetrahedral, but molecular geometry is pyramidal (trigonal pyramidal). This is pyramidal.

$$S_2O_7^{2-}$$ (disulphate / pyrosulphate):

Two $$SO_4$$ tetrahedra share one oxygen. Each S is in a tetrahedral environment. Not pyramidal.

Only 1 species ($$SO_3^{2-}$$) has pyramidal geometry.

The correct answer is Option (4): 1.