What is the valance bond theory?

Answer 1

Valence Bond Theory:

•

A discussion of valence bond theory is based on the knowledge of atomic

orbitals, electronic configuration of elements, overlap criteria of atomic

orbitals and principles of variation and superposition.

•

Orbital Overlap Concept of Covalent Bond: When two atoms approach

each other, partial merger of two bonding orbitals, known as overlapping

of the orbitals occurs.

•

Depending upon the type of overlapping, the covalent bonds may be

divided as sigma (H) bond and Pi (

p ) bond.

•

Sigma (H) bond: This type of covalent bond is formed by the end to end

(hand on) overlapping of bonding orbitals along the inter-nuclear axis.

The overlap is known as head on overlap or axial overlap. The sigma bond

is formed by any one of the following types of combinations of atomic

orbitals. Sigma (H) bond can be formed by

- s overlapping, s - p

overlapping,

p - p Overlapping etc.

•

Pi ( p ) Bond: This type of covalent bond is formed by the sidewise overlap

of the half- filled atomic orbitals of bonding atoms. Such an overlap is

known as sidewise or lateral overlap.

42. Hybridization:

•

In order to explain characteristic geometrical shapes of polyatomic

molecules concept of hybridization is used.

•

The process of intermixing of the orbitals of slightly different energies so

as to redistribute their energies resulting in the formation of new set of

orbitals of equivalent energies and shape.

43. Atomic orbitals used in different types of hybridization.

Shapes of

molecules/ions

Answer 2

It was proposed by PAULING for complexes. To explain metalligand bonding Pauling put forward new assumptions which is known as V B T . According to this theory :- Nature of Metal-ligand bond are purely covalent in nature. Central metal ion contains vaccant (n-1)d,ns,np and nd orbitals. LIgand contains lone pair which is full filled orbital. Central metal ion and ligand over lap to each other and produce metal-ligand bond. Covalent bond inwhich donar and acceptor species are found generally known as co-ordination bond here ligands are known as donar species and centrl metal is acceptor species. in other words metal-ligand bonding are special type of covalant bonding which is known as co-ordinate bond [Mn+ ..L]. Geometry of the complex ion depends upon the types nof overlaping or nature of overlaping. After overlaping of metal ligand- A. if an unpaired e- remains inthis complex then such type of complexea are called paramagnetic in nature. b. if all e- are paired then such complexs are dimagnetic and coloured.

Answer 3

The valence cell theory assumes that each atom in a molecule will achieve a geometry. It minimizes the repulsion between electrons in the valence shell of that atom.

Answer 4

ovalent bonds form by the overlap of the atomic nucleus

Answer 5

what is 1st postulate