Hybridization occurs when orbitals are in atomic theory mix to form new atomic orbitals. New orbitals can hold the same total number of electrons as the old ones. The properties and energy of the new hybridized orbitals are ‘averages’ from the original uncarbonized orbitals. The concept of hybridization was introduced because that is the best explanation for the fact that all C-H bonds in molecules such as methane are identical.
For example, in its basic state, carbon atoms naturally have an electron configuration of 1s 2 2s 2 2p 2 . Four outer electrons, i.e. those in the 2s and 2p sublevels are available to form chemical bonds with other atoms. 2s orbitals can hold up to two electrons, and there are three 2p orbitals, each capable of holding up to two electrons, which means that 2p orbitals can hold up to six electrons.
table of contents
- Definition of Hybridization
- Understanding Hybridization According to Experts
- Types of Hybridization and Examples
- Hybridization sp
- Sp2 hybridization
- Sp3 hybridization
- Sp3d hybridization
- Sp3d2 hybridization
- Sp3d3 hybridization
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- Definition of Hybridization
The chemist Linus Pauling first developed the theory of hybridization in 1931 to explain the structure of simple molecules such as methane (CH4) using atomic orbitals. Pauling shows that carbon atoms form four bonds using one and three p orbitals.
So it can be “concluded” that the carbon atom will form three bonds at right angles (using p orbitals) and the fourth weaker bond using s orbitals in the free direction.
In fact, methane has four bonds of equal strength separated by a tetrahedral bond angle of 109.5 °. Pauling explains this by supposing that in the presence of four hydrogen atoms, s and p orbitals form four equivalent combinations or hybrid orbitals, each symbolized by sp3 to show its composition, which is directed along the four CH bonds.
This concept was developed for simple chemical systems, but this approach was later applied more broadly, and today is considered an effective heuristic for rationalizing the structure of organic compounds. It provides a simple orbital image that is equivalent to Lewis’s structure.
The hybridization theory is an integral part of the meaning of organic chemistry , one of the most interesting examples is the Baldwin rule. To draw the reaction mechanism it is sometimes necessary to draw a classic bond with two atoms sharing two electrons.
The hybridization theory explains the bonding to alkenes and methane. The number of p characters, which is decided mainly by hybridization of orbitals, can be used to predict molecular properties such as acidity or basicity.
Definition of Hybridization
Hybridization can be interpreted as a series of processes combining orbitals from one atom with another atom when the meaning of a chemical bond occurs so as to achieve lower energy or high stability.
When two atoms will be chemically bonded, the two atoms need an empty orbital to be occupied by electrons from each of these atoms so that after binding, both atoms will occupy the same orbitals on their valence electrons. Therefore, in the hybridization process involves the configuration of electrons, especially the valence electrons used for binding.
Understanding Hybridization According to Experts
The definition of hybridization according to experts, among others, are as follows;
Hybridization is the idea that atomic orbitals combine to form newly hybridized orbitals, which in turn, affects molecular geometry and bonding properties. Hybridization is also an extension of valence bond theory.
In chemistry, hybridization of orbitals (or hybridization) is the concept of mixing atomic orbitals into new hybrid orbitals (with energy, shapes, etc., which are different from atomic orbital components) that are suitable for electron pairing to form chemical bonds in valence bond theory.
Types of Hybridization and Examples
Based on the types of orbitals involved in mixing, hybridization can be classified as sp3, sp2, sp, sp3d, sp3d2, sp3d3. The following is an explanation along with an example:
Sp hybridization is a combination of 1 s orbitals with 1 p orbitals so that there are 2 free p orbitals that are not used. Sp hybridization will produce three types of double bonds because there are 2 free p orbitals, each of which can produce phi bonds with other atomic orbitals so that overall this hybridization has 1 sigma bond and 2 phi bonds.
The result is that the bond strength is stronger than the other two hybridisations and the bond distance is also the shortest. The molecular shape produced by sp hybridization is linear with an angle of 180.
Examples of sp hybridization are, for example, Beryllium dichloride (BeCl 2 ). Beryllium has 4 orbitals and 2 electrons in the outer shell. In hybridization Beryllium 2s orbitals and one 2p orbitals on Be hybridized into 2 sp hybrid orbitals and 2p orbitals that are not tribridised. In addition to BeCl 2, sp hybridization also occurs in all other temperate components, such as BeF 2 , BeH 2.
Sp 2 hybridization is a combination of 1 s orbitals with 2 p orbitals so that there are 1 free p orbitals which are not used for hybridization. Sp 2 hybridization will produce a double bond type so that the bond strength is higher than the single bond and the resulting bond length is also shorter.
In sp 2 hybridization , double bonds can occur because there is 1 free p orbital that can form phi bonds with orbitals from other atoms. Sp 2 hybridization will produce a planar geometric shape with a bond angle of 120.
An example of sp 2 hybridization is assumed to occur in Boron trifluoride. Boron has 4 orbitals, but only 3 eletrons in the outer shell. Boron hybridization produces a combination of 2s and 2p orbitals into 3 sp2 hybrid orbitals and 1 orbital that do not undergo hybridization.
Sp 3 hybridization
Sp 3 hybridization is a hybridization that involves combining 1 s orbitals with 3 p orbitals consisting of p x , p y , and p z producing sp 3 that can be used to bind to four other atoms.
Sp 3 hybridization has the type of single bond or one sigma bond where the bond strength in this hybridization is the weakest among other hybridizations, while the bond length in this hybridization is the biggest among others. Molecules undergoing sp 3 hybridization will produce tetrahedral geometric shapes. Examples of sp 3 hybridization occur in ethane (C 2 H 6 ), methane (CH 4 ).
The 2s and 3p carbon orbitals hybridize to form four sp3 orbitals. These hybrid orbitals bind to four hydrogen atoms through overlapping sp3-s orbitals to produce CH 4 (methane).
Sp 3 hybridization d
Sp3d hybridization involves mixing 3p and 1d orbitals to form 5 sp3d hybridization orbitals with the same energy. They have trigonal bipyramidal geometry. The mixture of s, p and d orbitals forms trigonal bipyramidal symmetry.
Three hybrid orbitals are located in a horizontal plane that is inclined at an angle of 120 ° to each other known as the equatorial orbital. The two remaining orbitals are located in a vertical plane in the 90-degree plane of the equatorial orbit known as an axial orbital. Examples of this hybridization occur in Phosphorus pentachloride (PCl 5 ).
SP 3 d 2 hybridization
Sp 3 d 2 hybridization has 1s, 3p and 2d orbitals, which undergo mixing to form 6 identical sp3d2 hybrid orbitals. These six orbitals are directed to the octahedron angle. They tend to be at an angle of 90 degrees to each other.
For example, in SF 6 , one electron each from 3s and 3p orbitals is pushed into a 3d orbital. Six orbitals get hybridized to form six sp 3 d 2 hybrid orbitals . Each of these sp3d2 hybrid orbitals overlaps with 2p fluorine orbitals to form S-F bonds. Thus, the SF6 molecule has an octahedral structure. The dotted electrons represent the electrons of the F-atom.
Sp 3 d 3 hybridization
Mixing 1s, 3 p and 3 d-atomic orbitals to form seven hybrid orbitals that are equivalent to the same energy. This hybridization is known as sp3d3 hybridization. Seven sp 3 d 3 hybrid orbitals are directed to the angles of the pentagonal bipyramid.
These are not equivalent hybrid orbitals because five of them are directed to the angles of ordinary pentagons, while the remaining two are directed up and down the plane. Geometry is pentagonal bipyramidal and bond angles are 72 0 and 90 0 .
An example is the formation of IF7. In the IF7 molecule, the central atom is I.
53 I – 1s 2 , 2s 2 , 2p 6 , 3s 2 , 3p 6 , 4s 2 , 3d 10 , 4p 6 , 5s 2 , 4d 10 , 5p 5
Seven atomic orbitals (1, 3p and 3d orbitals) hybridize to form seven sp3d3 hybrid orbitals. This is filled in singly. These hybrid orbitals overlap with a single 2pz atomic orbitals filled with seven F atoms to form seven IF sigma bonds. IF7 geometry is pentagonal bipyramidal and bond angles are 72 0 and 90 0 .
In addition to the types of hybridization that have been mentioned above, there is a classification of hybridization that occurs in plants based on the taxonomic relationship of the two parents, which can be classified into two major groups, namely:
- Intervarietal Hybridization
Parents involved in hybridization include the same species; they may be two types, varieties or races of the same species. It is also known as intraspecific hybridization. In crop improvement programs, intervarietal hybridization is the most commonly used.
An example is the crossing of two varieties of wheat (T. aestivum), rice (O. Sativa) or other plants. Intervarietal crosses may be simple or complex depending on the number of parents involved.
- Simple Cross
Simple cross-hybridization includes intervarietal hybridization that occurs when two parents are traversed to produce F1. F1 independently to produce F2 or be used in a backcross program , e.g., A x B → F1 (A x B).
- Cross Complex
Simple cross-hybridization includes intervarietal hybridization that occurs when more than two parents are crossed to produce a hybrid, which is then used to produce F2 or used in backcross. Such crossing is also known as convergent crossing because this crossing program aims to unite genes from several parents into a single hybrid.
Three mains (A, B, C)
- Remote Hybridization
This includes crossing between different species of the same genus or different genera. When two species of the same genus are crossed, it is known as inter-specific hybridization; but when they belong to two different genera it is called intergenerational hybridization.
In general, the purpose of the crossing is to transfer one or several inherited characters such as resistance to plant species. Sometimes, interspecific hybridization can be used to develop new varieties.
For example, the Clinton wheat variety was developed from a cross between Avena sativa x A. byzantina (both haploid wheat species), and the CO 31 rice variety was developed from an Oryza sativa var cross. indica x O. perennis.