Name: chemical bonding and bond properties
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 2 min 37 s
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K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.3.1

Types of Chemical Bonds

Химические связи необходимы атомам для образования различных соединений, таких как соль, вода или сплавы. Понимание образования химической связи или, более конкретно, притяжения между атомами, поможет понять и предсказать поведение молекул. Ядро атома состоит из нейтронов и положительно заряженных протонов и окружено отрицательно заряженными электронами.Когда два атома приближаются друг к другу, электроны одного атома притягиваются к ядру другого атома и наоборот. Одновременно ядра обоих атомов отталкиваются друг от друга, как и электроны каждого атома. Когда эти взаимодействия приводят к общему снижению потенциальной энергии, образуется химическая связь.Есть три типа химических связей. Металл и неметалл, например натрий и хлор, образуют ионную связь. Металлы имеют низкую энергию ионизации, что облегчает отрыв электронов с атома.Эти электроны легко принимаются неметаллами из-за их высокого сродства к электрону и стремления достичь полной валентной оболочки. Следовательно, металл передает электроны неметаллу, образуя катион и анион. Эти заряженные частицы притягиваются друг к другу, создавая ионную связь.Второй тип это ковалентные связи, образованные между двумя неметаллами, такими как углерод и два атома кислорода, образующие диоксид углерода. Неметаллы имеют высокую энергию ионизации, что затрудняет отрыв и перенос валентных электронов от одного атома к другому, поэтому электроны распределяются между атомами. Эти общие электроны взаимодействуют с обоими ядрами связанных атомов и понижают потенциальную энергию.Последний тип это металлическая связь, образующаяся между двумя атомами металла. Атомы металлов легко теряют валентные электроны, образуя пул электронов согласно простейшей модели металлической связи. Валентные электроны становятся делокализованными по всему металлу, и положительно заряженные атомы металла притягиваются к этому пулу электронов, который удерживает атомы вместе.

Типы химических связей

< Теории химической связи были изобретены американским химиком Гилбертом Н. Льюисом. Он разработал модель, названную моделью Льюиса, чтобы объяснить тип и образование различных связей. Химическая связь занимает центральное место в химии; он объясняет, как атомы или ионы связываются вместе, образуя молекулы. Это объясняет, почему одни связи сильные, а другие слабые, или почему один углерод связывается с двумя атомами кислорода, а не с тремя; почему вода - это H 2 O, а не H 4 O. & nbsp; 
 
 <h4>Ионные связи </h4>
 
 Ионы - это атомы или молекулы, несущие электрический заряд. Катион (положительный ион) образуется, когда нейтральный атом теряет один или несколько электронов из своей валентной оболочки, а анион (отрицательный ион) образуется, когда нейтральный атом получает один или несколько электронов в своей валентной оболочке. Соединения, состоящие из ионов, называются ионными соединениями (или солями), а составляющие их ионы удерживаются вместе ионными связями: электростатическими силами притяжения между противоположно заряженными катионами и анионами. 
 
 Свойства ионных соединений проливают некоторый свет на природу ионных связей. Ионные твердые тела имеют кристаллическую структуру и имеют тенденцию быть жесткими и хрупкими; они также имеют высокие точки плавления и кипения, что говорит о том, что ионные связи очень прочны. Ионные твердые вещества также являются плохими проводниками электричества по той же причине — прочность ионных связей препятствует свободному перемещению ионов в твердом состоянии. Однако большинство ионных твердых частиц легко растворяются в воде. После растворения или расплавления ионные соединения являются превосходными проводниками электричества и тепла, так как ионы могут свободно перемещаться. 
 
 <h4>Ковалентные связи </h4>
 
 Неметаллические атомы часто образуют ковалентные связи с другими неметаллическими атомами. Ковалентные связи образуют, когда электроны разделены между атомами и притягиваются ядрами обоих атомов. Если атомы, образуя ковалентную связь, идентичны, как в H2, Cl2 и других двухатомных молекулах, то электроны в связи должны быть поделены поровну. Это называется чистой ковалентной связью. Когда атомы, связанные ковалентной связью, отличаются, связывание электронов разделено, но более не одинаково. Вместо этого, связывание электронов притягивается к одному атому больше, чем к другому, что приводит к смещению плотности электронов в сторону этого атома. Такое неравное распределение электронов известно как полярная ковалентная связь. 
 
 Соединения, содержащие ковалентные связи, имеют иные физические свойства, чем ионные соединения. Поскольку притяжение между молекулами, которые электрически нейтральны, слабее, чем между электрически заряженными ионами, ковалентные соединения, как правило, имеют гораздо более низкие точки плавления и кипения, чем ионные соединения. Кроме того, в то время как ионные соединения являются хорошими проводниками электричества при растворении в воде, большинство ковалентных соединений нерастворимы в воде; поскольку они электрически нейтральны, они являются плохими проводниками электричества в любом состоянии. 
 
 <h4>Металлические связи </h4>
 
 Металлические связи образуются между двумя атомами металла. Пол Дрюде разработал упрощенную модель для описания металлического связывания, которая называется «Модель электронного моря». На основе низкой энергии ионизации металлов модель заявляет, что атомы металлов легко теряют свои валентные электроны и становятся катионами. Эти валентные электроны создают море делокализованных электронов, окружающих катионы по всему металлу.  
 
 Металлические твердые частицы, такие как кристаллы меди, алюминия и железа, образуются атомами металла, и все они обладают высокой теплопроводностью и электропроводностью, металлическим блеском и ковальностью. Многие из них очень твёрдые и довольно прочные. Из-за своей ковкости (способности к деформации под давлением или при ударе) они не раскалываются и, следовательно, делают используются в производстве полезных строительных материалов. Точки плавления металлов сильно различаются. Ртуть является жидкостью при комнатной температуре, а щелочные металлы расплавляются при температуре ниже 200 °C. Несколько металлов после перехода также имеют низкие точки плавления, в то время как переходные металлы плавляются при температурах выше 1000 °C. Эти различия отражают различия в прочности металлического соединения между металлами.  
 
 Этот текст адаптирован из <a href=""https://openstax.org/books/chemistry-2e/pages/7-1-ionic-bonding"">Openstax, Химия 2е изд., раздел 7.1: Ионные связи</a>, <a href=""https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding"">Openstax, Химия 2е изд., раздел 7.2: Ковалентные связи</a>, и <big><a href=""https://openstax.org/books/chemistry-2e/pages/10-5-the-solid-state-of-matter"">Openstax, Химия 2е изд., раздел 10.5: Твердое состояние вещества</a>. </big>

Теории химических связей были впервые предложены американским химиком Гилбертом Н. Льюисом. Он разработал модель, названную моделью Льюиса, чтобы объяснить тип и...

Education

JoVE Core

Химия

Один

Chemical Bonding: Basic Concepts

Химическая связь: основные понятия

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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

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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

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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

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Motion and Stability: Forces and Interactions

CHEM1.PS2.1

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CH.3.d

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Arizona Science Standards

HS.P1

HS.P1U1.2

HS+C.P1

HS+C.P1U1.4

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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

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New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-3.

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HS-PS1-2.

HS-PS1-4.

HS-PS1-12.

Georgia Standards of Excellence

SPS2.

Chemical Bonds

SC2.

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Bonding Types: From Nonpolar Covalent to Ionic

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Chemical Bonding and Bond Properties

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