Question

which pair consists of molecules having the same geometry?

	PCl3 and BF3
	CH2O and CH3OH
	CH2CCl2 and CH2CH2
	CO2 and SO2

Answer 1

Concepts and reason

The shape of the molecule is represented as its geometry. There are two types of geometry exhibited by the molecule with respect to lone pair electrons of atoms present in the molecule.

• Electron pair geometry

• Molecular geometry

Fundamentals

Electron pair geometry:

Electron pair geometry gives the shape for the molecule by considering both bond pair and lone pair electrons in the molecule.

Example:

The oxygen atom in the water molecule contains 2 lone pair electrons. The water molecule has a tetrahedral geometry by considering both lone pair and bond pair electrons.

Molecular geometry:

The three-dimensional structure of the molecule is represented as molecular geometry. The molecular geometry considers only bond pair of electrons. It does not consider lone pair electrons.

Example:

The molecular geometry of water molecule is bent. It does not consider the lone pair electrons in the molecule.

The compounds ${\rm{PC}}{{\rm{l}}_{\rm{3}}}$ and ${\rm{B}}{{\rm{F}}_{\rm{3}}}$ do not contain the same geometry. Because ${\rm{PC}}{{\rm{l}}_{\rm{3}}}$ shows a trigonal pyramidal geometry and ${\rm{B}}{{\rm{F}}_{\rm{3}}}$ shows trigonal planar geometry.

The compounds ${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{O}}$ and ${\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{OH}}$ do not show the same geometry. Because, ${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{O}}$ shows trigonal planar geometry and ${\rm{C}}{{\rm{H}}_{\rm{3}}}{\rm{OH}}$ shows tetrahedral geometry.

The compounds ${\rm{C}}{{\rm{O}}_{\rm{2}}}$ and ${\rm{S}}{{\rm{O}}_{\rm{2}}}$ does not show the same geometry because ${\rm{C}}{{\rm{O}}_{\rm{2}}}$ shows linear shape and ${\rm{S}}{{\rm{O}}_{\rm{2}}}$ shows bent shape.

The compounds ${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{CC}}{{\rm{l}}_{\rm{2}}}$ and ${\rm{C}}{{\rm{H}}_{\rm{2}}}{\rm{C}}{{\rm{H}}_{\rm{2}}}$ show the same geometry, as both compounds shows trigonal planar geometry.

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