Name: chemical bonds: types and strength
Uploaded: 2023-04-30T18:28:31.000Z
Duration: 2 min 40 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-1

Chemical Bonds

当原子相互靠近时，它们的原子核会相互排斥，电子之间也会相互排斥。与此同时，每个原子的电子会被另一个原子的原子核吸引，并以一种方式排列，使得原子间的吸引力最大化，同时使排斥力最小化。
如果这导致净吸引力，则系统的势能降低。这种相互作用称为化学键。
然而，并非每种原子组合都能形成稳定的化学键。原子的化学性质主要取决于其成键方式以及所形成化学键的类型。理解构成化合物的原子之间的成键情况，有助于认识和预测其分子行为。
键能是指断裂1摩尔气态化合物中某一化学键所需的能量。它取决于成键原子的种类以及参与成键的电子数目。键能越大，化学键的强度越高。
成键原子的种类以及参与成键的电子数目也会影响键长，键长是指两个成键原子核之间的平均距离，其数值与键级和键能成反比。
最常见的化学键相互作用介于离子键和共价键之间，形成一个连续谱系：离子键涉及带相反电荷的离子之间的静电吸引，而共价键则通过原子间共享价电子形成。
离子键是离子化合物中主要存在的相互作用。构成化合物的阳离子和阴离子通过静电吸引力结合在一起。通常，离子的形成伴随着参与反应的原子之间价电子的转移。
失去电子的原子成为阳离子，而获得电子的原子则成为阴离子。电子的转移通常使每个离子达到最近的稀有气体电子构型，即通过电子数目最小的变化所达到的构型，从而使离子在能量上更加稳定。
在共价键中，共享的电子与成键原子的原子核相互作用，从而降低势能。双键和三键分别在原子之间共享两对和三对电子。由于这增加了受到另一个原子核额外吸引力作用的电子数量，因此键的强度随着键级的增加而增强。

化学键

原子参与化学键的形成，以获得完整的价层电子构型，类似于原子序数最接近的惰性气体的价电子构型。 离子键、共价键和金属键是一些重要的化学键类型。 键能和键长决定化学键的强度。

 <h4>化学键的类型</h4>

 离子键由于阳离子和阴离子之间的静电引力而形成。 通常，离子的形成是通过一个原子的电子转移到另一个原子来实现的。 然而，这些键没有明确的方向性，因为静电吸引力均匀分布在整个三维空间中。


 共价键是相邻原子之间共享电子对形成的化学键。 共享的电子对称为键合对。 共价键具有方向性。


 两个金属原子之间形成金属键。 金属结合由"电子海模型"描述。 基于金属的低电离能，该模型指出金属原子很容易失去价电子并成为阳离子。 这些价电子在整个金属上的阳离子周围形成了离域电子池。


 <h4>键能和键长</h4>


 共价键的强度是通过破坏共价键所需的能量来衡量的，即分离键合原子所需的能量。 分离任何一对键合原子都需要能量。 化学键越牢固，打破它所需的能量就越大。


 打破一摩尔气体分子中特定共价键所需的能量称为键能或键解离能。 双原子分子的键能定义为吸热反应的标准焓变。 具有三个或更多原子的分子具有两个或多个键。 这种分子中所有键能的总和等于破坏分子中所有键的吸热反应的标准焓变。


 两个原子之间的键强度随着电子对数量的增加而增强。 一般来说，两个原子之间的键数越多，键长越短，键强度越大。 因此，相同两个原子之间的三键比双键更强且更短; 同样，双键比单键更强且更短。 当一个原子与一组中的不同原子键合时，键合强度通常会随着组的向下移动而降低。


 本文改编自 <a href="https://openstax.org/books/chemistry-2e/pages/7-1-ionic-bonding">Openstax, Chemistry 2e, Section 7.1: Ionic Bonding</a>, <a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, Section 7.2: Covalent Bonding</a>, <a href="https://openstax.org/books/chemistry-2e/pages/10-5-the-solid-state-of-matter">Section 10.5: The Solid State of Matter</a>, and Section<a href="https://openstax.org/books/chemistry-2e/pages/7-5-strengths-of-ionic-and-covalent-bonds"> 7.5. Bond Strength: Covalent Bonds

原子通过参与化学键的形成，以获得与最邻近的稀有气体相似的完整价层电子构型。

Education

教育

JoVE Core

Organic Chemistry

有机化学

Unit 1

第一单元

Covalent Bonding and Structure

共价键与结构

KEY TERMS AND CONCEPTS

关键术语与概念

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 covalent bond forms when adjacent atoms share electron pairs. The shared pair is called the bonding pair. Covalent bonds are directional, so the atoms are linked in a specific orientation.

A metallic bond forms between two metal atoms. The electron sea model describes this type of bonding. In this model, metal atoms lose valence electrons easily and become cations, while the delocalized electrons form a pool around the cations across the metal.

The strength of a covalent bond is measured by the energy needed to break it and separate the bonded atoms. Stronger bonds require more energy. For one mole of gaseous molecules, this value is called bond energy, or bond dissociation energy. For a diatomic molecule, it is the standard enthalpy change for the endothermic reaction that breaks the bond.

Molecules with three or more atoms have more than one bond. In those cases, the total bond energy is the sum of all bond energies needed to break every bond in the molecule. Bond strength also increases as the number of electron pairs in the bond increases. Triple bonds are stronger and shorter than double bonds between the same atoms, and double bonds are stronger and shorter than single bonds. When one atom bonds to different atoms in a group, bond strength usually decreases as you move down the group.

Chemical Bonds: Types and Strength

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chemical bonds

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polar covalent bonds

Electronegativity in Polar Covalent Bonds

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key terms and concepts

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organic chemistry

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9-12

Physical Geology

Minerals

Chemical bonding (ionic, covalent, metallic)

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HS-PS1-4

Chemical Bonds: Types and Strength

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