How to find hybridisation electronic distribution-?
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This picture is an image of a Centaur from Sphinx Stargate. The Centaur is a race of monsters in Greek mythology, hybrid animal having the head, arms and torso of a man united to the body and legs of a horse. Mixing a number of atomic orbitals to form the same number of hybrid orbitals to explain chemical bonding and shapes and molecular structures is a rather recent myth.
The most significant development in the first half of the 20th century is the human's ability to understand the structure of atoms and molecules. Computation has made mathematical concepts visible to the extent that we now can see the atomic and molecular orbitals. On the other hand, Using everyday encountered materials or toys can also generate beautiful illustrations of hybrid atomic orbitals.
The valence bond (VB) approach is different from the molecular orbital (MO) theory. Despite their differences, most of their results are the same, and they are interesting.
The valence bond (VB) theory
The valence-bond approach considers the overlap of the atomic orbitals (AO) of the participation atoms to form a chemical bond. Due to the overlapping, electrons are localized in the bond region.
The overlapping AOs can be of different types, for example, a sigma bond may be formed by the overlapping the following AOs.
Chemical bonds formed due to overlap of atomic orbitals
s-s s-p s-d p-p p-d d-d
H-H
Li-H H-C
H-N
H-F H-Pd in
palladium
hydride C-C
P-P
S-S F-S
in SF6 Fe-Fe
However, the atomic orbitals for bonding may not be "pure" atomic orbitals directly from the solution of the Schrodinger Equation. Often, the bonding atomic orbitals have a character of several possible types of orbitals. The methods to get an AO with the proper character for the bonding is called hybridization. The resulting atomic orbitals are called hybridized atomic orbitals or simply hybrid orbitals.
We shall look at the shapes of some hybrid orbitals first, because these shapes determine the shapes of the molecules.
Hybridization of atomic orbitals
The solution to the Schrodinger Equation provides the wavefunctions for the following atomic orbitals:
1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, etc.
For atoms containing two or more electrons, the energy levels are shifted with respect to those of the H atom. An atomic orbital is really the energy state of an electron bound to an atomic nucleus. The energy state changes when one atom is bonded to another atom.
Quantum mechanical approaches by combining the wave functions to give new wavefunctions are called hybridization of atomic orbitals. Hybridization has a sound mathematical fundation, but it is a little too complicated to show the details here. Leaving out the jargons, we can say that an imaginary mixing process converts a set of atomic orbitals to a new set of hybrid atomic orbitals or hybrid orbitals.
At this level, we consider the following hybrid orbitals:
sp
sp2
sp3
sp3d
sp3d2
The sp hybrid atomic orbitals
The sp hybrid atomic orbitals are possible states of electron in an atom, especially when it is bonded to others. These electron states have half 2s and half 2p characters. From a mathematical view point, there are two ways to combine the 2s and 2p atomic orbitals:
sp1 = 2s + 2p
sp2 = 2s - 2p
These energy states (sp1 and sp2) have a region of high electron probability each, and the two atomic orbitals are located opposite to each other, centered on the atom. The sp hybrid orbitals are represented by this photograph.
H-Be-H 1s 1s
H sp1 Be sp2 H
1s 1s
For example, the molecule H-Be-H is formed due to the overlapping of two 1s orbitals of 2 H atoms and the two sp hybridized orbitals of Be. Thus, the H-Be-H molecule is linear. The diagram here shows the overlapping of AOs in the molecule H-Be-H.
The ground state electronic configuration of Be is 1s22s2, and one may think of the electronic configuration "before" bonding as 1s2sp2. The two electrons in the sp hybrid orbitals have the same energy.
Linear molecules
ClBeCl
HCCH
HCN
O=C=O
You may say that the concept of hybridizing AOs for the bonding is just a story made up to explain the molecular shape of Cl-Be-Cl. You are right! The story is lovely and interesting, though.
In general, when two and only two atoms bond to a third atom and the third atom makes use of the sp hybridized orbitals, the three atoms are on a straight line. For example, sp hybrid orbitals are used in the central atoms in the molecules shown on the right.
The sp2 hybrid orbitals
The energy states of the valence electrons in atoms of the second period are in the 2s and 2p orbitals. If we mix two of the 2p orbitals with a 2s orbital, we end up with three sp2 hybridized orbitals. These three orbitals lie on a plane, and they point to the vertices of a equilateral triangle as shown here.
When the central atom makes use of sp2 hybridized orbitals, the compound so formed has a trigonal shape. BF3 is such a molecule:
Molecules with sp2 Hybrid orbitals
F
|
B
/ \
F F . . -2
:O:
|
C
/ \\
:O:: O
.
N
// \\
O O
. .
O
// \\
O O
. .
S
// \\
O O
The most significant development in the first half of the 20th century is the human's ability to understand the structure of atoms and molecules. Computation has made mathematical concepts visible to the extent that we now can see the atomic and molecular orbitals. On the other hand, Using everyday encountered materials or toys can also generate beautiful illustrations of hybrid atomic orbitals.
The valence bond (VB) approach is different from the molecular orbital (MO) theory. Despite their differences, most of their results are the same, and they are interesting.
The valence bond (VB) theory
The valence-bond approach considers the overlap of the atomic orbitals (AO) of the participation atoms to form a chemical bond. Due to the overlapping, electrons are localized in the bond region.
The overlapping AOs can be of different types, for example, a sigma bond may be formed by the overlapping the following AOs.
Chemical bonds formed due to overlap of atomic orbitals
s-s s-p s-d p-p p-d d-d
H-H
Li-H H-C
H-N
H-F H-Pd in
palladium
hydride C-C
P-P
S-S F-S
in SF6 Fe-Fe
However, the atomic orbitals for bonding may not be "pure" atomic orbitals directly from the solution of the Schrodinger Equation. Often, the bonding atomic orbitals have a character of several possible types of orbitals. The methods to get an AO with the proper character for the bonding is called hybridization. The resulting atomic orbitals are called hybridized atomic orbitals or simply hybrid orbitals.
We shall look at the shapes of some hybrid orbitals first, because these shapes determine the shapes of the molecules.
Hybridization of atomic orbitals
The solution to the Schrodinger Equation provides the wavefunctions for the following atomic orbitals:
1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, etc.
For atoms containing two or more electrons, the energy levels are shifted with respect to those of the H atom. An atomic orbital is really the energy state of an electron bound to an atomic nucleus. The energy state changes when one atom is bonded to another atom.
Quantum mechanical approaches by combining the wave functions to give new wavefunctions are called hybridization of atomic orbitals. Hybridization has a sound mathematical fundation, but it is a little too complicated to show the details here. Leaving out the jargons, we can say that an imaginary mixing process converts a set of atomic orbitals to a new set of hybrid atomic orbitals or hybrid orbitals.
At this level, we consider the following hybrid orbitals:
sp
sp2
sp3
sp3d
sp3d2
The sp hybrid atomic orbitals
The sp hybrid atomic orbitals are possible states of electron in an atom, especially when it is bonded to others. These electron states have half 2s and half 2p characters. From a mathematical view point, there are two ways to combine the 2s and 2p atomic orbitals:
sp1 = 2s + 2p
sp2 = 2s - 2p
These energy states (sp1 and sp2) have a region of high electron probability each, and the two atomic orbitals are located opposite to each other, centered on the atom. The sp hybrid orbitals are represented by this photograph.
H-Be-H 1s 1s
H sp1 Be sp2 H
1s 1s
For example, the molecule H-Be-H is formed due to the overlapping of two 1s orbitals of 2 H atoms and the two sp hybridized orbitals of Be. Thus, the H-Be-H molecule is linear. The diagram here shows the overlapping of AOs in the molecule H-Be-H.
The ground state electronic configuration of Be is 1s22s2, and one may think of the electronic configuration "before" bonding as 1s2sp2. The two electrons in the sp hybrid orbitals have the same energy.
Linear molecules
ClBeCl
HCCH
HCN
O=C=O
You may say that the concept of hybridizing AOs for the bonding is just a story made up to explain the molecular shape of Cl-Be-Cl. You are right! The story is lovely and interesting, though.
In general, when two and only two atoms bond to a third atom and the third atom makes use of the sp hybridized orbitals, the three atoms are on a straight line. For example, sp hybrid orbitals are used in the central atoms in the molecules shown on the right.
The sp2 hybrid orbitals
The energy states of the valence electrons in atoms of the second period are in the 2s and 2p orbitals. If we mix two of the 2p orbitals with a 2s orbital, we end up with three sp2 hybridized orbitals. These three orbitals lie on a plane, and they point to the vertices of a equilateral triangle as shown here.
When the central atom makes use of sp2 hybridized orbitals, the compound so formed has a trigonal shape. BF3 is such a molecule:
Molecules with sp2 Hybrid orbitals
F
|
B
/ \
F F . . -2
:O:
|
C
/ \\
:O:: O
.
N
// \\
O O
. .
O
// \\
O O
. .
S
// \\
O O
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