Name: chemical bonding and bond properties
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 2 min 37 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.1

Types of Chemical Bonds

化学键对于原子形成各种化合物，例如盐、水或合金等来说至关重要。了解化学键的形成，或更具体地说：原子间的吸引力，有助于理解和预测分子行为。原子核由中子 和带正电的质子组成，或被带负电的电子包围。当两个原子向彼此靠近时，来自一个原子的电子会被吸引 到另一个原子的核，反之亦然。同时，两个原子的核彼此排斥，同样地各原子的电子也是。当这些相互作用导致净重减少时，势能的一部分会形成化学键。化学键分为三种。金属和非金属，例如離子鍵上的鈉和氯，形成离子键。金属的离子能很低，使电子更容易从原子中被去除。这些电子很容易 被具有高电子亲和力、并渴望 获得完整价壳的非金属接受。因此，金属将电子转移到非金属 形成阳离子和阴离子。这些带电粒子相互吸引 产生离子键。第二种是共价键，其形成于两种非金属间，例如碳和两个氧原子 形成二氧化碳。非金属具有高离子能，使价电子难以 从一个原子到另一个原子转移。因此電子會在原子之間被共享。这些共享的电子与键的两个原子核相互作用 并降低其势能。最后一种是两个金属原子之间 形成的金属粘接。金属原子容易失去价电子，并形成一个最简易形式的 电子池。价电子 在这整个金属和带正电的金属原子上 会因为被电子池吸引而移位，将原子结合在一起。

化学键的类型

化学键合理论是由美国化学家吉尔伯特·路易斯（Gilbert N. Lewis）提出的。他开发了一个称为路易斯模型的模型来解释不同键的类型和形成。化学键对化学至关重要。它解释了原子或离子如何结合在一起形成分子。它解释了为什么有些键强而有些键弱，或者为什么一个碳键与两个氧键而不是三个氧键。为什么水是H 2 O而不是H 4 O。
 
 <h4>离子键</ h4>
 
 离子是带有电荷的原子或分子。当中性原子从其化合价壳中失去一个或多个电子时，会形成阳离子（正离子），而当中性原子在其化合价壳中获得一个或多个电子时，会形成阴离子（负离子）。由离子组成的化合物称为离子化合物（或盐），其组成离子通过离子键（带相反电荷的阳离子和阴离子之间的静电吸引力）保持在一起。
 
 离子化合物的性质为离子键的性质提供了一些启示。离子固体表现出晶体结构，并且往往是刚性和脆性的；它们也往往具有较高的熔点和沸点，这表明离子键非常牢固。出于同样的原因，离子固体也是电的不良导体-离子键的强度会阻止离子在固态中自由移动。但是，大多数离子型固体很容易溶于水。离子化合物一旦溶解或熔化，便是电和热的极好导体，因为离子可以自由移动。
 
 <h4>共价键</ h4>
 
 非金属原子经常与其他非金属原子形成共价键。当电子在原子之间共享并被两个原子的原子核吸引时，就会形成共价键。如果形成共价键的原子相同，如H 2 ，Cl 2 和其他双原子分子，则该键中的电子必须相等地共享。这被称为纯共价键。当通过共价键连接的原子不同时，键合电子共享，但不再相等。取而代之的是，键合电子比另一个原子更容易吸引到一个原子上，从而导致电子密度朝那个原子移动。电子的这种不均匀分布被称为极性共价键。
 
 含有共价键的化合物表现出与离子化合物不同的物理性质。因为电中性的分子之间的吸引力弱于带电离子之间的吸引力，所以共价化合物的熔点和沸点通常比离子化合物低得多。此外，尽管离子化合物溶于水时是良好的电导体，但大多数共价化合物不溶于水；由于它们是电中性的，因此在任何状态下都是不良的导体。
 
 <h4>金属键</ h4>
 
 在两个金属原子之间形成金属键。保罗·德勒（Paul Dr＆uuml; de）已开发出一种描述金属结合的简化模型，称为“电子海模型”。基于金属的低电离能，该模型指出金属原子容易失去其价电子并成为阳离子。这些价电子在整个金属上形成围绕阳离子的离域电子池。
 
 金属固体，例如铜，铝和铁的晶体。由金属原子形成，并且它们都显示出高的导热性和导电性，金属光泽和延展性。许多人非常努力，也很坚强。由于它们的可延展性（在压力或锤击下变形的能力），它们不会破碎，因此可制成有用的建筑材料。金属的熔点差异很大。汞在室温下为液体，碱金属在200℃以下熔化。几种过渡金属也具有低熔点，而过渡金属在高于1000℃的温度下熔化。这些差异反映了金属之间金属结合强度的差异。
 
 此文本改编自<a href="https://openstax.org/books/chemistry-2e/pages/7-1-ionic-bonding">Openstax, 化学2e, 第7.1节：离子键</a>, <a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, 化学2e, 第7.2节：共价键</a>, 和 <big><a href="https://openstax.org/books/chemistry-2e/pages/10-5-the-solid-state-of-matter">Openstax, 化学2e, 第10.5节：物质的固态状态</a>.</big>

化学键理论由美国化学家吉尔伯特·N·路易斯（Gilbert N. Lewis）率先提出。他建立了一种称为路易斯模型的理论，用于解释化学键的类型及……

Education

教育

JoVE Core

化学

Chemical Bonding: Basic Concepts

化学键：基本概念

KEY TERMS AND CONCEPTS

关键术语与概念

chemical bonding and bond properties

Chemical bonding explains how atoms and ions join to form molecules and compounds. American chemist Gilbert N. Lewis pioneered chemical bonding theory with the Lewis model. This model helps explain why bonds form, why some are stronger than others, and why compounds have fixed formulas like H2O instead of H4O.

Ionic bonding involves ions, which are atoms or molecules with an electrical charge. A cation is a positive ion formed when a neutral atom loses one or more electrons from its valence shell. An anion is a negative ion formed when a neutral atom gains one or more electrons in its valence shell. Ionic compounds, also called salts, are held together by electrostatic attraction between oppositely charged cations and anions.

The properties of ionic compounds show why ionic bonds are strong. Ionic solids usually have a crystalline structure and are rigid and brittle. They also tend to have high melting and boiling points. In the solid state, they are poor conductors of electricity because the ions cannot move freely. Many ionic solids dissolve readily in water. When they are dissolved or melted, they conduct electricity and heat well because the ions can move about freely.

Covalent bonding is common between nonmetal atoms. It forms when atoms share electrons, and the shared electrons are attracted by the nuclei of both atoms. When identical atoms bond, as in H2 and Cl2, the electrons are shared equally. This is called a pure covalent bond. When different atoms bond, the electrons are still shared, but not equally. This creates a polar covalent bond, where electron density shifts toward one atom.

Covalent compounds have different properties from ionic compounds. Because the attraction between neutral molecules is weaker than the attraction between charged ions, covalent compounds usually have much lower melting and boiling points. Most are insoluble in water. They are also poor conductors of electricity in any state because they are electrically neutral.

Metallic bonding forms between metal atoms. Paul Drude's electron sea model describes this bond by saying that metal atoms lose valence electrons easily and become cations. The valence electrons form a pool of delocalized electrons around the cations throughout the metal. Metallic solids, such as copper, aluminum, and iron, conduct heat and electricity well. They also have metallic luster and are malleable, so they can deform under pressure or hammering without shattering.

Metals can have very different melting points. Mercury is liquid at room temperature, and alkali metals melt below 200 degrees Celsius. Several post-transition metals also have low melting points. Transition metals, however, melt above 1000 degrees Celsius. These differences reflect differences in the strength of metallic bonding among metals.

Chemical Bonding and Bond Properties

types of chemical bonds

Chemical bonding explains how atoms and ions join to form molecules and compounds. American chemist Gilbert N. Lewis pioneered chemical bonding theory with the Lewis model. This model helps explain why bonds form, why some are stronger than others, and why compounds have fixed formulas like H2O instead of H4O. Ionic bonding involves ions, which are atoms or molecules with an electrical charge. A cation is a positive ion formed when a neutral atom loses one or more electrons from its valence...

the born-haber cycle

Predicting Ionic Stability with Lattice Energy

Lattice energy helps explain why ionic compounds are stable. It measures the strength of attraction between positive and negative ions in a crystal. In one common definition, lattice energy is the energy required to separate one mole of an ionic solid into gaseous ions, so it has a positive value. Another definition uses the opposite sign and describes the energy released when gaseous ions form a lattice. When checking data, it is important to confirm which convention is being used. In either...

lewis symbols and the octet rule

Valence Electrons, Lewis Symbols, and Bonding

Chemical bonds form when atoms or ions interact in ways that lower the potential energy of a molecule. Gilbert N. Lewis created a simple model to show bond formation using valence electrons, the electrons in the outer shell. In this model, electrons are shared or transferred to help atoms reach a stable electron configuration. The Lewis model helps describe two common bond types. An ionic bond forms when electrons move from a metal to a nonmetal. A covalent bond forms when two nonmetals share...

electronegativity

Electronegativity and Polar Bonds

Electronegativity helps explain why some covalent bonds are nonpolar and others are polar covalent. It is a measure of how strongly an atom attracts shared electrons toward itself. That pull controls how electron density is distributed in a bond. Linus Pauling proposed the first electronegativity values by studying bond energies in heteronuclear molecules such as hydrogen fluoride. He expected the bond energy of HF to be about the average of the bond energies of H2 and F2, or 296 kJ/mol. The...

ionic bonding and electron transfer

Ionic Compounds and Crystal Lattices

Ionic compounds form when positive and negative ions attract each other. A cation is a positive ion, and it forms when an atom loses one or more valence electrons. An anion is a negative ion, and it forms when an atom gains one or more valence electrons. Compounds made of these ions are called ionic compounds, or salts, and the force between them is an ionic bond. The properties of ionic solids help show how strong this attraction is. They usually form rigid, brittle crystals and have high...

trends in lattice energy: ion size and charge

trends-in-lattice-energy-ion-size-and-charge

Lattice Energy Patterns in Ionic Solids

Lattice energy shows how strongly ions hold an ionic solid together. It is the energy required to separate one mole of a solid into its gaseous ions. For sodium chloride, this process requires 769 kJ per mole. The opposite convention may also be used, where lattice energy is the energy released when gaseous ions form the solid. In either case, a larger magnitude means a more stable ionic compound. For ionic crystals, lattice energy follows a pattern based on charge and ion size. The...

covalent bonding and lewis structures

Shared Electrons in Covalent Molecules

Covalent molecules form when atoms share electrons instead of transferring them. This bonding usually happens between nonmetal atoms with similar tendencies to attract electrons. Because the atoms pull on the electrons in a shared way, the bond is held together by mutual attraction. Covalent compounds often have physical properties that differ from ionic compounds. The attraction between neutral molecules is weaker than the attraction between charged ions. As a result, many covalent compounds...

bond polarity, dipole moment, and percent ionic character

bond-polarity-dipole-moment-and-percent-ionic-character

How Bond Polarity Shapes Molecular Dipoles

Bond polarity depends on electronegativity, the ability of an atom to attract shared electrons. The absolute value of the electronegativity difference, or ΔEN, gives a rough guide to bond type. When the difference is very small or zero, the bond is covalent and nonpolar. When it is larger, the bond may be polar covalent or ionic. Examples show how this works in real compounds. H–H has a ΔEN of 0, so it is nonpolar. H–Cl has a ΔEN of 0.9, so it is polar covalent. Na–Cl has a ΔEN of 2.1, so it...

lewis structures of molecular compounds and polyatomic ions

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Drawing Lewis Structures with Valence Electron Counts

Drawing Lewis structures starts with counting valence electrons and building the atom arrangement step by step. Valence electrons are the outer-shell electrons that help show how atoms bond. For ions, a positive charge means one electron is removed for each plus sign, and a negative charge means one electron is added for each minus sign. The next step is to sketch the skeleton structure. The least electronegative atom usually goes in the center, while hydrogen is almost never central. Fluorine...

resonance

Resonance Forms in Lewis Structures

Resonance forms in Lewis structures help explain molecules and ions that cannot be shown correctly with just one drawing. In nitrite ion, NO2−, the Lewis structure can be drawn in two ways. The N-O and N=O bonds switch positions in the two drawings, but the atoms stay in the same arrangement. If nitrite really had one single bond and one double bond, the two bond lengths should be different. A double bond is shorter and stronger than a single bond between the same atoms. Experiments show that...

formal charges

Lewis Structures with Formal Charge

Lewis structures can sometimes show more than one reasonable arrangement for a molecule or polyatomic ion. Formal charge helps chemists choose the best Lewis structure when that happens. It is a useful way to compare possible structures in chemistry. Formal charge is the hypothetical charge an atom would have if bonding electrons were shared evenly between the atoms. It can also be found by starting with the valence electrons of the neutral atom, subtracting the nonbonding electrons, and then...

exceptions to the octet rule

Octet Rule Exceptions in Lewis Structures

Some covalent molecules do not follow the octet rule in their Lewis structures. Their central atoms can fall into three groups: odd-electron molecules, electron-deficient molecules, and hypervalent molecules. These cases show why a Lewis structure may not always give every atom eight valence electrons. Odd-electron molecules have an odd number of valence electrons, so one electron remains unpaired. Molecules with an odd number of electrons are called radicals. Nitric oxide, NO, is one example,...

bond energies and bond lengths

How Bond Energy Predicts Reaction Heat

Bond energy helps explain why molecules stay together and how much heat a reaction may release or absorb. A covalent bond is stronger when more energy is needed to separate the atoms. The energy needed to break one specific covalent bond in one mole of gaseous molecules is called bond energy, or bond dissociation energy. For a diatomic molecule, bond energy is the standard enthalpy change for an endothermic reaction that breaks that bond. The H-H bond is a common example. Its bond energy is...

bonding in metals

Electron Sea Model in Metals

Electron sea model explains how metallic bonding holds metals together. In this model, most metal atoms do not have enough valence electrons to form ionic or covalent bonds in the usual way. Their valence electrons are held loosely because metals have low electronegativity, and their ionization energy is low, so electrons are removed easily. When a metal atom loses these outer electrons, it becomes a positively charged metal ion. The freed electrons form a delocalized electron cloud around...

key terms and concepts

Explore ionic, covalent, and metallic bonding, plus the properties of each. Learn how electrons, ions, and metals explain structure, conductivity, and melting points.

Chemical Bonding and Bond Properties | JoVE K12

chemistry

JoVE Core 化学通过简单明了且通俗易懂的动画视频课程，将普通化学概念带入到现实生活当中。此外，在科学家行动视频中，我们演示了在实验室中进行的经典和原始研究实验。

Physical Science

PS.PSc.2.1

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Bonding and compounds

Structure And Properties Of Matter

Chemical bonding

Physical Geology

Minerals

Chemical bonding (ionic, covalent, metallic)

Tennessee Academic Standards

High School

Matter and Its Interactions

CHEM1.PS1.14

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

CHEM1.PS2.1

CHEM1.PS2.2

Virginia  Standards of Learning

HIgh School

CH.3

CH.3.d

PS.3

PS.3.c

Minnesota Academic Standards in Science

1.2.1 9C.1.2.1.2

Arizona Science Standards

HS.P1

HS.P1U1.2

HS+C.P1

HS+C.P1U1.4

Texas Essential Knowledge and Skills

CHEM.6

CHEM.6.E

Alabama Course of Study Science

9-12.C.2.2.a

9-12.C.2.2.c

Florida Department of Education

SC.912.P.8

SC.912.P.8.6

Chemistry and Physics

IPC.7

IPC.7.A

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-3.

HS. Chemical Reactions

HS-PS1-2.

HS-PS1-4.

HS-PS1-12.

Georgia Standards of Excellence

SPS2.

Chemical Bonds

SC2.

bonding-types-from-nonpolar-covalent-to-ionic

Bonding Types: From Nonpolar Covalent to Ionic

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Radioactive Decay and Radiometric Dating

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Nuclear Power

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The Energies of Atomic Orbitals

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The Aufbau Principle and Hund's Rule

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Electron Configuration of Multielectron Atoms

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PS.Chm.1.3

Periodic Classification of the Elements

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The Periodic Table

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PS.Chm.2.1

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PS.Chm.2.2

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Chemical Bonding and Bond Properties

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