In chemistry, hybridisation is the mixing of atomic orbitals to form new orbitals suitable for bonding. Hybridisation is an integral part of the valence shell electron-pair repulsion (VSEPR) theory as well as a quantum mechanical model for orbital electrons to describe groups 2,3,4 of the periodic families of elements whose electron orbital clouds fuse into one hybrid orbital. Groups 1,5,6 and 7 in the period table do not hybridise. The hybridisation theory was theorised by chemist Linus Pauling in order to explain the existence of molecules such as methane (CH₄). The problem with the existence of methane is this: It is made up of a carbon atom bonded to four hydrogen atoms. Carbon's ground-state configuration is 1s² 2s² 2p_x¹ 2p_y¹ or perhaps more easily read: Chemistry (in Greek: χημεία) is the science of matter and its interactions with energy and itself (see physics, biology). ... Electron atomic and molecular orbitals In quantum mechanics, the states of an atom, i. ... Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ... Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ... Generally, an element is a basic part that is the foundation of something. ... A chemist is a scientist who specializes in chemistry. ... Linus Carl Pauling (February 28, 1901 – August 19, 1994) was an American physical chemist, widely regarded as the premier chemist of the twentieth century. ... A molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... In physics, the ground state of a quantum mechanical system is its lowest-energy state. ...

(Note: The 1s orbital is lower in energy than the 2s orbital, and the 2s orbital is lower in energy than the 2p orbitals)

The valence bond theory would predict, based on the existence of two half-filled p-type orbitals (the designations p_x p_y or p_z are meaningless at this point, as they do not fill in any particular order), that C forms two covalent bonds. CH₂, however, is known as a methylene group and cannot exist outside of a molecular system. Therefore, this theory alone cannot explain the existence of CH₄. The valence bond theory considers the overlap of the atomic orbitals of the participation atoms to form a chemical bond. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... In chemistry, methylene is di-valent functional group CH2 derived formally from methane. ...

Furthermore, ground state orbitals cannot be used for bonding in CH₄. While exciting a 2s electron into a 2p orbital would theoretically allow for four bonds, according to the valence bond theory which has been proved experimentally correct for systems like O₂ this would imply that the various bonds of CH₄ would have differing energies due to differing levels of orbital overlap. Once again, this has been experimentally disproved: any hydrogen can be removed from a carbon with equal ease.

To summarise, to explain the existence of CH₄ and many other molecules a method by which as many as 12 bonds (for transition metals) of equal strength (and therefore equal length) can be created is required. This article is in need of attention. ...

One approach to this is the concept of hybridisation. Historically, this concept was necessary in order to explain the bonding observed in very simple chemical systems. It was later found to be more widely applicable, and today it is considered an effective heuristic for understanding organic chemistry. It is less applicable to other branches of chemistry for which the heavier atoms are involved. Transition metal chemistry is one example. Hybridisation schemes in transition metal chemistry tend to be more sophisticated because the assumptions have to be somewhat more relaxed for hybridisation to be useful. As a consequence, this results in a more complicated theory of hybridisation for transition metals - but one in fact which is not very accurate and has little predictive power. The result of this was a development of entirely new branches of bonding theory, and these are an active area of theoretical chemical research today. Organic chemistry is the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds that by definition contain carbon. ...

It is important to note that orbitals are a model representation of how an electron around an atom behaves. In the case of simple hybridization, this approximation is based on the atomic orbitals of hydrogen. Hybridised orbitals are assumed to be different mixtures of these atomic orbitals, superimposed on each other in various different proportions. Hydrogen orbitals are used as a basis for simple schemes of hybridisation because it is one of the few examples of orbitals for which an exact analytic solution to its Schrödinger equation is known. These orbitals are then assumed to be slightly, but not significantly distorted in heavier atoms, like carbon, nitrogen, and oxygen. Under these assumptions is the theory of hybridisation most applicable. In physics, the Schrödinger equation, proposed by the Austrian physicist Erwin Schrödinger in 1925, describes the time-dependence of quantum mechanical systems. ...

The first step in hybridisation is the excitation of one (or more) electrons. From this point of the explanation on, it can be assumed that the subject of study is carbon in the context of methane, for simplicity. The proton that forms the nucleus of a hydrogen atom attracts one of the valence electrons on carbon. This causes an excitation, moving a 2s electron into a 2p orbital. This, however, increases the influence of the carbon nucleus on the valence electrons by increasing the effective core potential (the amount of charge the nucleus exerts on a given electron = Charge of Core - Charge of all electrons closer to the nucleus). General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ...

The combination of these forces creates new mathematical functions known as hybridised orbitals. In the case of carbon attempting to bond with four hydrogens, four orbitals are required. Therefore, the 2s orbital (core orbitals are almost never involved in bonding) mixes with the three 2p orbitals to form four sp³ hybrids (read as s p three). See graphical summary below.

becomes

In CH₄, four sp³ hybridised orbitals are overlapped by hydrogen's 1s orbitals, yielding four sigma (σ) bonds. The four bonds are of the same length and strength, and there are four of them. This theory fits our requirements. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Geometry of the water molecule Molecules have fixed equilibrium geometries--bond lengths and angles--that are dictated by the laws of quantum mechanics. ...

translates into My feeble attempt at drawing methane in terms of hybrid orbitals File links The following pages link to this file: Orbital hybridisation Categories: GFDL images ... My feeble attempt at drawing methane in terms of structure File links The following pages link to this file: Orbital hybridisation Categories: GFDL images ...

Other C-compounds and other molecules may be explained similarly, for example ethene (C₂H₄). Carbon will never form any less than four bonds unless it is given no other choice, which seldom occurs. Therefore, ethene has two double bonds between the carbons. The Lewis structure looks like this: Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ...

from rozeta This image is ineligible for copyright and therefore in the public domain, because it consists entirely of information that is common property and contains no original authorship. ...

Carbon will sp² hybridise, because hybrid orbitals will form only sigma bonds and one pi bond is required for the double bond between the carbons. The hydrogen-carbon bonds are all of equal strength and length, which agrees with experimental data. Electron atomic and molecular orbitals, showing a Pi-bound at the bottom left of the picture In chemistry, pi bonds (Ï€ bonds) are bonds with a single nodal plane containing the line segment between the two species. ... Covalently bonded hydrogen and carbon in a molecule of methane. ...

Molecule shape

Hybridisation helps to explain molecule shape.

• AX₂ (eg, BeCl₂): sp hybridisation; linear or digonal shape
• AX₃ (eg, BCl₃): sp² hybridisation; trigonal planar shape
• AX₄ (eg, CCl₄): sp³ hybridisation; tetrahedral shape
• AX₅ (eg, PCl₅): sp³d hybridisation; trigonal bipyramidal shape
• AX₆ (eg, SF₆): sp³d² hybridisation; octahedral (or square bipyramidal) shape

This holds if there are no lone electron pairs on the central atom. If there are, they should be counted in the X_i number. For example, in water (H₂O), the oxygen atom has two bonds with H and two lone electron pairs (as can be seen with the valence bond theory as well from the electronic configuration of oxygen), which means there are four such 'elements' on O. The model molecule is, then, AX₄: sp³ hybridisation is utilised, and the electron arrangement of H₂O is tetrahedral. The shape, however, is non-linear bent, since lone electron pairs are not visible, and also because repulsions must be taken into account. The HOH angle is round about 104.5 degrees. A line, or straight line, is, roughly speaking, an (infinitely) thin, (infinitely) long, straight geometrical object, i. ... For alternate meanings, such as the musical instrument, see triangle (disambiguation). ... In mathematics, a plane is the fundamental two-dimensional object. ... A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. ... For alternate meanings, such as the musical instrument, see triangle (disambiguation). ... A bipyramid is a polyhedron formed by joining two identical pyramids base-to-base. ... An octahedron (plural: octahedra) is a polyhedron with eight faces. ... A square as a geometric shape is described and illustrated at square (geometry). ... A bipyramid is a polyhedron formed by joining two identical pyramids base-to-base. ... Water (from the Old English word wæter; c. ... This article is about the chemical element oxygen. ...

See also

• Linear combination of atomic orbitals molecular orbital method