Name: covalent bond overlap and orbital hybridization
Uploaded: 2025-05-22T09:05:33.000Z
Duration: 2 min 38 s
Channel: JoVE

Valence bond theory proposes that a chemical bond results through an overlap of partially filled atomic orbitals, including those other than the spherical s orbital.
When a single bond forms between two non-spherical orbitals, the two orbitals will have head-to-head overlap.
The type of covalent bond formed by head-to-head overlap of atomic orbitals is called a sigma bond.
s and p orbitals overlapping to form covalent bonds cannot yield the various molecular shapes in the VSEPR model. Valence bond theory helps to explain this molecular geometry through the hybridization, or mixing, of atomic orbitals.
Some atomic orbitals involved in bonding recombine to form new orbitals whose shapes are a hybrid of the originals. The initial number of atomic orbitals and the number of hybrid orbitals generated is always the same.
The hybrid orbitals have a different shape from their constituent atomic orbitals, with one lobe that is significantly larger than the other. Thus, the electron probability density is highly concentrated in a directional lobe, which leads to a more effective overlap with the orbitals of other atoms. For clarity, these orbitals are often shown without the minor lobes.
For instance, in the excited state of carbon, the one s and three p orbitals that contain the four unpaired electrons undergo hybridization, yielding four equivalent hybrid s-p-three orbitals that occupy the vertices of a regular tetrahedron.
The mixing of one s and two p orbitals in the excited state of carbon generates three equivalent s-p-two hybrid orbitals with trigonal planar geometry.
Similarly, the hybridization of one s and one p orbital can create two sp orbitals oriented at 180 degrees to each other.&#160;&#160;
The concept of hybridization also provides an explanation for the formation of multiple bonds. The side-on overlap of two p orbitals gives rise to a pi bond.
However, a pi bond can only be formed in double and triple bonds when a sigma bond already exists between two atoms. Because the pi bond exists on opposite sides of the internuclear axis, pi bonds are unable to rotate around this axis.

valence bond theory and hybridized orbitals

Valence Bond Theory and Hybridized Orbitals

According to valence bond theory, a covalent bond results when: (1) an orbital on one atom overlaps an orbital on a second atom, and (2) the single electrons in each orbital combine to form an electron pair. The strength of a covalent bond depends on the extent of overlap of the orbitals involved. Maximum overlap is possible when the orbitals overlap on a direct line between the two nuclei.
A &#963; bond (single bond in a Lewis structure) is a covalent bond in which the electron density is concentrated in the region along the internuclear axis. A &#960; bond is a covalent bond that results from the side-by-side overlap of two p orbitals. In a &#960; bond, the regions of orbital overlap lie on opposite sides of the internuclear axis, while there is a node (a plane with no probability of finding an electron) along the axis. All single bonds are &#963; bonds, while multiple bonds consist of both &#963; and &#960; bonds.
When atoms are bound together in a molecule, the wave functions for atomic orbitals can combine to produce new mathematical descriptions that have different shapes. This process is called hybridization and is mathematically accomplished by the linear combination of atomic orbitals. The resulting new orbitals are called hybrid orbitals.
The shapes and orientations of hybrid orbitals, which are formed only in covalently bonded atoms, are different from those of atomic orbitals in isolated atoms. The number of hybrid orbitals is equal to the number of atomic orbitals that were combined to generate them. All orbitals in a set of hybrid orbitals are equivalent in shape and energy, and their orientation is predicted by the VSEPR theory. Hybrid orbitals overlap to form &#963; bonds, while unhybridized orbitals overlap to form &#960; bonds.
For instance, in the excited state of carbon, the one 2s and three 2p orbitals undergo hybridization yielding four degenerate hybrid sp3 orbitals oriented tetrahedrally. In a methane molecule, the 1s orbital of each of the four hydrogen atoms overlaps with one of the four sp3 orbitals of the carbon atom to form a sigma (&#963;) bond.
Similarly, the mixing of one 2s and two of the 2p orbitals of carbon generates three equivalent sp2 hybrid orbitals with trigonal planar geometry, while the hybridization of one 2s and one of the 2p orbitals creates two sp orbitals oriented at 180&#176; to each other.
For atoms that have d orbitals in their valence subshells, hybridization of five valence shell atomic orbitals (one s, three p, and one of the d orbitals) gives five sp3d hybrid orbitals with trigonal bipyramidal geometry. An octahedral arrangement of six hybrid orbitals is obtained by the mixing of six valence shell atomic orbitals (one s, three p, and two of the d orbitals), which yields six sp3d2 hybrid orbitals.
This text has been adapted from&#160;<a href="https://openstax.org/books/chemistry-2e/pages/8-1-valence-bond-theory">Openstax, Chemistry 2e, Section 8.1 Valence Bond Theory</a>&#160;and&#160;<a href="https://openstax.org/books/chemistry-2e/pages/8-2-hybrid-atomic-orbitals">Section 8.2 Hybrid Atomic Orbitals</a>.

According to valence bond theory, a covalent bond results when: (1) an orbital on one atom overlaps an orbital on a second atom, and (2) the single ...

valence-bond-theory-and-hybridized-orbitals

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Organic Chemistry

Unit 1

Covalent Bonding and Structure

KEY TERMS AND CONCEPTS

covalent bond overlap and orbital hybridization

Covalent bonds form when orbitals on two atoms overlap and their single electrons pair up. The bond is stronger when the overlap is greater. Maximum overlap happens when the orbitals meet along a direct line between the two nuclei.

A sigma bond, or σ bond, is the kind of covalent bond found in a single bond in a Lewis structure. In a σ bond, electron density is concentrated along the internuclear axis. A pi bond, or π bond, forms when two p orbitals overlap side by side. In a π bond, the overlap lies on opposite sides of the internuclear axis, and a node with no electron probability lies along the axis. Single bonds are σ bonds, while multiple bonds include both σ and π bonds.

When atoms join in a molecule, atomic orbital wave functions can combine to make new orbital shapes. This process is called hybridization, and it is described by the linear combination of atomic orbitals. The new orbitals are called hybrid orbitals. They form only in covalently bonded atoms, and their shapes and orientations differ from those of atomic orbitals in isolated atoms. The number of hybrid orbitals matches the number of atomic orbitals used to make them. Orbitals in one hybrid set have the same shape and energy, and their directions follow VSEPR theory. Hybrid orbitals form σ bonds, while unhybridized orbitals form π bonds.

Carbon shows this pattern clearly. In its excited state, one 2s orbital and three 2p orbitals hybridize to form four equivalent sp3 orbitals arranged tetrahedrally. In methane, each hydrogen 1s orbital overlaps with one carbon sp3 orbital to make a σ bond. One 2s orbital and two 2p orbitals can also mix to make three equivalent sp2 orbitals with trigonal planar geometry. When one 2s orbital mixes with one 2p orbital, two sp orbitals form and point 180° apart.

Atoms with d orbitals in the valence shell can form larger hybrid sets. Mixing five valence shell atomic orbitals, one s, three p, and one d, gives five sp3d hybrid orbitals with trigonal bipyramidal geometry. Mixing six valence shell atomic orbitals, one s, three p, and two d, gives six sp3d2 hybrid orbitals with octahedral geometry.

Covalent Bond Overlap and Orbital Hybridization

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Covalent bonds form when orbitals on two atoms overlap and their single electrons pair up. The bond is stronger when the overlap is greater. Maximum overlap happens when the orbitals meet along a direct line between the two nuclei. A sigma bond, or σ bond, is the kind of covalent bond found in a single bond in a Lewis structure. In a σ bond, electron density is concentrated along the internuclear axis. A pi bond, or π bond, forms when two p orbitals overlap side by side. In a π bond, the...

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Learn how orbital overlap forms sigma and pi bonds, then see how hybridization creates sp3, sp2, sp, sp3d, and sp3d2 orbitals in molecules.

Covalent Bond Overlap and Orbital Hybridization | JoVE K12

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Covalent Bond Overlap and Orbital Hybridization

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