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

価電子結合理論は、化学結合は、球面のs軌道以外のものを含む、部分的に満たされた原子軌道の重なりによって生じることを提案しています。
2つの非球面軌道の間に単一の結合が形成されると、2つの軌道は頭と頭が重なります。
原子軌道の直接と頭の重なりによって形成される共有結合のタイプは、シグマ結合と呼ばれます。
s軌道とp軌道が重なり合って共有結合を形成すると、VSEPRモデルのさまざまな分子形状を生成できません。原子価結合理論は、原子軌道のハイブリダイゼーションまたは混合を通じて、この分子形状を説明するのに役立ちます。
結合に関与する一部の原子軌道は、再結合して、元の軌道のハイブリッド形状の新しい軌道を形成します。原子軌道の初期数と生成される混成軌道の数は常に同じです。
混成軌道は、その構成する原子軌道とは異なる形状をしており、一方の葉が他方の葉よりも大幅に大きい。したがって、電子確率密度は指向性ローブに高度に集中し、他の原子の軌道とより効果的にオーバーラップします。わかりやすくするために、これらの軌道はしばしばマイナーローブなしで示されます。
例えば、炭素の励起状態では、4つの不対電子を含む1つのs軌道と3つのp軌道が混成され、正四面体の頂点を占める4つの等価なs-p-three軌道が生成されます。
炭素の励起状態で1つのs軌道と2つのp軌道を混合すると、三方晶平面形状の3つの等価なs-p-twoハイブリッド軌道が生成されます。
同様に、1つのs軌道と1つのp軌道の混成により、互いに180度を向いた2つのsp軌道を作成できます。 
ハイブリダイゼーションの概念は、複数の結合の形成についても説明します。2つのp軌道のサイドオンオーバーラップにより、pi結合が生じます。
ただし、π結合は、2つの原子間にシグマ結合がすでに存在する場合にのみ、二重結合と三重結合で形成できます。π結合は核間軸の反対側に存在するため、π結合はこの軸を中心に回転できません。

原子価結合理論と混成軌道

Valence Bond Theory and Hybridized Orbitals

原子価結合理論によれば、共有結合は、(1) 1 つの原子の軌道が 2 番目の原子の軌道と重なり、(2) 各軌道の単一電子が結合して電子対を形成する場合に生じます。 共有結合の強さは、関与する軌道の重なりの程度によって異なります。 軌道が 2 つの原子核間の直線上で重なる場合、最大の重なりが可能になります。
σ 結合（ルイス構造における単結合）は、核間軸に沿った領域に電子密度が集中している共有結合です。 π 結合は、2 つの p 軌道が隣り合って重なり合うことによって生じる共有結合です。 π 結合では、軌道の重なり合う領域が核間軸の反対側にあり、軸に沿ってノード（電子が見つかる可能性のない平面）が存在します。 すべての単結合は σ 結合ですが、多重結合は σ 結合と π 結合の両方で構成されます。
原子が分子内で結合すると、原子軌道の波動関数が結合して、異なる形状を持つ新しい数学的記述が生成されます。 このプロセスは混成と呼ばれ、原子軌道の線形結合によって数学的に達成されます。 結果として生じる新しい軌道は、混成軌道と呼ばれます。
共有結合した原子のみで形成される混成軌道の形状と方向は、孤立した原子の原子軌道とは異なります。 混成軌道の数は、混成軌道を生成するために結合された原子軌道の数と同じです。 混成軌道のセット内のすべての軌道は、形状とエネルギーが同等であり、それらの配向は VSEPR 理論によって予測されます。 混成軌道は重なって σ 結合を形成し、混成されていない軌道は重なって π 結合を形成します。
たとえば、炭素の励起状態では、1 つの 2s 軌道と 3 つの 2p 軌道が混成化して四面体形に配向した 4 つの縮退混成 sp3 軌道が生成されます。 メタン分子では、4 つの水素原子のそれぞれの 1s 軌道が炭素原子の 4 つの sp3 軌道の 1 つと重なり、シグマ (σ) 結合を形成します。
同様に、炭素の 1 つの 2s 軌道と 2 つの 2p 軌道の混合により、平面三角形をもつ 3 つの等価な sp2 混成軌道が生成されますが、1 つの 2s 軌道と 2p 軌道の 1 つの混成により、互いに 180° の方向を向いた 2 つの sp 軌道が生成されます。
価電子サブシェルに d 軌道を持つ原子の場合、5 つの価電子シェル原子軌道 (1 つの s、3 つの p、および d 軌道の 1 つ) の混成により、三角両錐形状の 5 つの sp3d 混成軌道が得られます。 6 つの混成軌道の八面体配置は、6 つの価電子殻原子軌道 (1 つの s、3 つの p、および 2 つの d 軌道) の混合によって得られ、6 つの sp3d2 混成軌道が得られます。
本文は、Openstax、Chemistry 2e、セクション 8.1「原子価結合理論」およびセクション 8.2「混成原子軌道」から編集したものです。

原子価結合理論によれば、共有結合は、(1)1つの原子の軌道が2番目の原子の軌道と重なり、(2)単一の...

valence-bond-theory-and-hybridized-orbitals

Education

JoVE Core

Organic Chemistry

有機化学

Unit 1

ユニット1

Covalent Bonding and Structure

共有結合と構造

KEY TERMS AND CONCEPTS

主要用語と概念

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

covalent-bond-overlap-and-orbital-hybridization

what is organic chemistry?

Carbon Compounds in Everyday Life

Organic chemistry focuses on carbon compounds called organic compounds. These compounds may come from living things or be made by chemists. Carbon is the main element in them, and it bonds with other carbon atoms as well as hydrogen, oxygen, nitrogen, and sulfur. Carbon can form up to four strong bonds. That ability lets carbon atoms build chains and rings of many sizes, shapes, and levels of complexity. Not every carbon-containing substance is classified as organic. Carbonates, cyanides, and...

electronic structure of atoms

Atomic Orbitals and Quantum Numbers

Atomic orbitals and quantum numbers describe how electrons are arranged around the nucleus. An atom has a small, positively charged nucleus with electrons surrounding it. The nucleus contains protons and neutrons, and the quantum mechanical model gives a better picture of this structure than older models. Protons carry a +1 charge and have a mass of 1.0073 amu. Neutrons have no charge and have a mass of 1.0087 amu. Electrons carry a −1 charge and have a mass of 0.00055 amu. The number of...

electron configurations

How Electrons Fill Atomic Orbitals

Electron filling in atoms follows a set order based on orbital energy. The Aufbau principle says each new electron enters the lowest-energy subshell available. The Pauli exclusion principle says no two electrons can share the same set of four quantum numbers. Hund’s rule of maximum multiplicity says electrons stay unpaired in equal-energy orbitals when possible. The order of filling follows the relative energies of the subshells. A common sequence is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.

chemical bonds

Chemical Bonds: Types and Strength

Chemical bonds help atoms reach a full valence shell like the nearest noble gas. The main bond types are ionic, covalent, and metallic. Bond energy and bond length also help explain how strong a bond is. An ionic bond forms from electrostatic attraction between cations and anions. In many cases, one atom transfers electrons to another atom, and the ions form from that transfer. Ionic bonds have no defined direction because the attraction spreads evenly through three-dimensional space. A...

polar covalent bonds

Electronegativity in Polar Covalent Bonds

Polar covalent bonds form when atoms share electrons unevenly. This happens in covalent bonds between atoms that have similar, but not identical, tendencies to attract electrons. Nonmetal atoms often make these bonds with other nonmetals. Hydrogen gas, H2, is a simple example of a covalent bond between two hydrogen atoms. A covalent bond begins when two atoms move close enough for their valence orbitals to overlap. In hydrogen, the 1s orbitals overlap and the single electrons on each atom...

lewis structures and formal charges

Lewis Structures, Bonds, and Formal Charge

Lewis structures show how atoms share electrons in covalent bonds and in polyatomic ions. Lewis symbols help draw these structures, and the periodic table helps predict how many valence electrons an atom has and how many bonds it can form to reach an octet. Group 18 elements, such as argon and helium, already have filled electron configurations. They rarely take part in chemical bonding. Atoms in group 17, such as bromine and iodine, need one more electron to reach an octet, so they can form...

vsepr theory

Molecular Shapes from Electron Pairs

Molecular shape can be predicted from the way electron pairs arrange around a central atom. Valence shell electron-pair repulsion theory, or VSEPR theory, uses a Lewis structure to count bonding pairs and lone electron pairs. The main idea is simple: electron pairs spread out as far as possible to reduce repulsion. In a molecule, the valence electrons around the central atom can be bonding pairs or lone pairs. Bonding pairs are found mainly between bonded atoms. Lone pairs stay on one atom and...

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Predicting Shape and Molecular Polarity

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Resonance in Nitrite and Carbonate Ions

Resonance explains why some Lewis structures do not match the measured properties of a molecule or ion. When two or more Lewis structures have the same atom arrangement, the real electron distribution is an average of the structures shown. The nitrite anion, NO2−, is one example. It can be drawn in two ways, with the N–O and N=O bonds in different places. If nitrite had one single bond and one double bond, the two bond lengths should be different, because a double bond is shorter and stronger...

valence bond theory and hybridized orbitals

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...

mo theory and covalent bonding

Bond Order and Molecular Orbitals

Molecular orbital theory explains how electrons are arranged in molecules. It treats electron regions in a molecule much like atomic orbitals in an atom. A molecular orbital is the region of space where a valence electron is most likely to be found. Molecular orbitals form through the linear combination of atomic orbitals, or LCAO. When atomic wave functions combine in phase, they create regions with high electron density. When they combine out of phase, they create nodes, or regions with no...

intermolecular forces and physical properties

intermolecular-forces-and-physical-properties

How Intermolecular Forces Affect Matter

Intermolecular forces are the attractions between molecules, and they help explain how matter behaves. These forces influence melting points, boiling points, and whether substances mix with one another. Water has a much higher boiling point than hexane, which shows that water has stronger intermolecular forces. Three main kinds of intermolecular interactions are covered here. They include ion-dipole forces, dipole-dipole interactions, and van der Waals forces, which include London dispersion...

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introduction to functional groups

Functional Groups and Organic Molecules

Functional groups are groups of atoms with specific chemical properties that appear within organic molecules. They are sometimes shown as "R." These groups sit along the carbon backbone of macromolecules, which can form chains or rings of carbon atoms. Functional groups help functionalize a compound. That means they can give the molecule different physical and chemical properties. In organic chemistry, this change in group structure can strongly affect how a compound behaves. Common...

overview of advanced functional groups

Advanced Functional Groups in Organic Chemistry

Advanced functional groups are atom clusters in organic molecules that give those molecules specific chemical properties. They are sometimes shown as "R" in formulas. By changing the atoms attached to a carbon skeleton, a functional group can make a compound behave differently in physical and chemical reactions. This topic covers several major classes of organic compounds with advanced functional groups. Aromatic hydrocarbons include benzene. Phenol is another example and is also called...

key terms and concepts

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

organic chemistry

JoVE Core 有機化学では、立体化学、反応、メカニズムの基本概念を、簡潔でわかりやすいアニメーション ビデオ レッスンを使用して説明します。さらに、科学者の実際のビデオでは、世界中の今日の研究室で行われている古典的および独自の研究実験における関連概念の適用を示しています。

Covalent Bond Overlap and Orbital Hybridization

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