Question

Explain in your own words the Molecular structure for multi center molecules.

Answer 1

# The molecules that have more than one central atom are called as multi center molecules.The structure that includes placements of atoms is called molecular structure and this influences the physical and chemical preoperty of the molecules.

# Molecular structures are in 3 dimension and it also includes bond angle(the angle between 2 bonds) and bond distance (the distance between two bonds) parameters in its representation.

# VSEPR theory (valence shell electron pair repulsion) helps in understanding the shapes and structures of multi center molecules.

#The basic assumptions of this theory is that pairs of electrons present in valence shell repel each other.These pairs helps in maximising in the distance between them.

The order of repulsion is as below:

lone pair - lone pair>lone pair-bonding pair>bonding pair - bonding pair.

Let us see the structure of some multi center molecules and their molecule type.Molecule types are terms using A and B for the atoms and E is used in denoting the number of lone pair of electons present in the molecule.eg: H2O is termed as AB₂E₂ as it has 1 oxygen(A), 2 hydrogen(B) and 2 lone pairs of electron(E). This representation of molecular types makes it easier to determine the structure of the molecules.

Molecule type	no: of bonding pairs	No: of lone pairs	Structure of molecule	Geometric Shape
AB4E	4	1	Trigonal bi-pyramidal	See saw
AB3E2	3	2	Trigonal bi -pyramidal	T-shaped
AB5E	5	1	Octahedral	Square pyramid
AB4E2	4	2	Octahedral	Square planar
AB2E	2	1	Trigonal planar	Bent
AB3E	3	1	Tetrahedral	Trigonal pyramidal
AB2E2	2	2	Tetrahedral	Bent

# Examples of bent shaped trigonal planar is SO2,O₃

Bent tetrahedral is water

see saw shaped trigonal bi-pyramidal is ClF₃

Square planar shaped octahedral is XeF₄

# The angles in between bonds of molecule in :

Octahedral=90or180

Trigonal bipyramidal=90or120

Tetrahedral=109