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

Wiązania chemiczne są niezbędne, aby atomy mogły tworzyć różne związki, takie jak sól, woda lub stopy. Zrozumienie tworzenia wiązań chemicznych, a dokładniej przyciągania między atomami, pomoże zrozumieć i przewidzieć zachowanie molekularne. 

Jądro atomu składa się z neutronów i dodatnio naładowanych protonów, które jest otoczone ujemnie naładowanymi elektronami. 

Kiedy dwa atomy zbliżają się do siebie, elektrony z jednego atomu są przyciągane do jądra drugiego atomu i odwrotnie. Jednocześnie jądra obu atomów odpychają się od siebie, podobnie jak elektrony każdego atomu.

Kiedy te oddziaływania prowadzą do redukcji netto energii potencjalnej, powstaje wiązanie chemiczne. Istnieją trzy rodzaje wiązań chemicznych.

Metal i niemetal, takie jak sód i chlor, tworzą wiązanie jonowe. Metale mają niskie energie jonizacji, co pozwala na łatwiejsze usuwanie elektronów z atomu. Elektrony te są łatwo akceptowane przez niemetale, biorąc pod uwagę ich wysokie powinowactwo elektronowe i chęć uzyskania pełnej powłoki walencyjnej.

Dlatego metal przenosi elektrony do niemetalu, tworząc kation i anion. Te naładowane cząstki przyciągają się nawzajem, tworząc wiązanie jonowe. 

Drugi typ to wiązania kowalencyjne utworzone między dwoma niemetalami, takimi jak węgiel i dwa atomy tlenu tworzące dwutlenek węgla. 

Niemetale mają wysokie energie jonizacji, co utrudnia usuwanie i przenoszenie elektronów walencyjnych z jednego atomu na drugi;  stąd elektrony są współdzielone między atomami. Te wspólne elektrony oddziałują z obydwoma jądrami wiążących atomów i obniżają energię potencjalną. 

Ostatnim typem jest wiązanie metaliczne powstające między dwoma atomami metalu. Atomy metalu łatwo tracą elektrony walencyjne, tworząc pulę elektronów zgodnie z najprostszym modelem morza elektronowego. 

Elektrony walencyjne ulegają delokalizacji na całym metalu, a dodatnio naładowane atomy metalu są przyciągane do tej puli elektronów, która utrzymuje atomy razem.

rodzaje wiązań chemicznych

Pionierem teorii wiązań chemicznych był amerykański chemik Gilbert N. Lewis. Opracował model zwany modelem Lewisa, aby wyjaśnić rodzaj i powstawanie różnych wiązań. Wiązanie chemiczne ma kluczowe znaczenie w chemii, gdyż wyjaśnia, w jaki sposób atomy lub jony łączą się ze sobą, tworząc cząsteczki. Mówi też, dlaczego niektóre wiązania są mocne, a inne słabe, dlaczego jeden węgiel wiąże się z dwoma atomami tlenu, a nie z trzema, czy dlaczego woda to H2O, a nie H4O.

<h4>Wiązania jonowe</h4>

Jony to atomy lub cząsteczki posiadające ładunek elektryczny. Kation (jon dodatni) powstaje, gdy neutralny atom traci jeden lub więcej elektronów ze swojej powłoki walencyjnej, a anion (jon ujemny) tworzy się, gdy neutralny atom zyskuje jeden lub więcej elektronów na swojej powłoce walencyjne9j. Związki składające się z jonów nazywane są związkami jonowymi (lub solami), a jony ich składowe są utrzymywane razem za pomocą wiązań jonowych: elektrostatycznych sił przyciągania pomiędzy przeciwnie naładowanymi kationami i anionami.

Właściwości związków jonowych rzucają nieco światła na naturę wiązań jonowych. Jonowe ciała stałe mają strukturę krystaliczną, są sztywne i kruche; mają również zwykle wysokie temperatury topnienia i wrzenia, co sugeruje, że wiązania jonowe są bardzo silne. Z tego samego powodu ciała stałe jonowe są również słabymi przewodnikami prądu elektrycznego — siła wiązań jonowych uniemożliwia swobodny ruch jonów w stanie stałym. Jednakże większość substancji stałych jonowych łatwo rozpuszcza się w wodzie. Po rozpuszczeniu lub stopieniu związki jonowe są doskonałymi przewodnikami prądu i ciepła, ponieważ jony mogą się swobodnie poruszać.

<h4>Wiązania kowalencyjne</h4>

Atomy niemetali często tworzą wiązania kowalencyjne z innymi atomami niemetali. Wiązania kowalencyjne powstają, gdy elektrony są dzielone między atomami i są przyciągane przez jądra obu atomów. Jeśli atomy tworzące wiązanie kowalencyjne są identyczne, jak w przypadku H2, Cl2 i innych cząsteczek dwuatomowych, wówczas elektrony w wiązaniu muszą być równomiernie rozdzielone. Nazywa się to czystym wiązaniem kowalencyjnym. Kiedy atomy połączone wiązaniem kowalencyjnym są różne, elektrony wiążące są wspólne, ale nie są już jednakowe. Zamiast tego elektrony wiążące są bardziej przyciągane do jednego atomu niż do drugiego, co powoduje przesunięcie gęstości elektronów w stronę tego atomu. Ten nierówny rozkład elektronów nazywany jest polarnym wiązaniem kowalencyjnym.

Związki zawierające wiązania kowalencyjne wykazują inne właściwości fizyczne niż związki jonowe. Ponieważ przyciąganie między cząsteczkami, które są elektrycznie obojętne, jest słabsze niż między jonami naładowanymi elektrycznie, związki kowalencyjne mają na ogół znacznie niższe temperatury topnienia i wrzenia niż związki jonowe. Ponadto, podczas gdy związki jonowe są dobrymi przewodnikami prądu elektrycznego po rozpuszczeniu w wodzie, większość związków kowalencyjnych jest nierozpuszczalna w wodzie; ponieważ są elektrycznie obojętne, są słabymi przewodnikami prądu elektrycznego w każdym stanie.

<h4>Wiązania metaliczne</h4>

Wiązania metaliczne powstają pomiędzy dwoma atomami metali. Paul Drüde opracował uproszczony model opisujący wiązania metaliczne, zwany „Modelem Morza Elektronowego”. Bazując na niskich energiach jonizacji metali, model stwierdza, że atomy metali łatwo tracą swoje elektrony walencyjne i stają się kationami. Te elektrony walencyjne tworzą pulę zdelokalizowanych elektronów otaczających kationy w całym metalu.

Metaliczne ciała stałe, takie jak kryształy miedzi, aluminium i żelaza. zbudowane są z atomów metali i wszystkie wykazują wysoką przewodność cieplną i elektryczną, metaliczny połysk i plastyczność. Wiele z nich jest bardzo twardych i dość silnych. Ze względu na swoją plastyczność (zdolność do odkształcania się pod wpływem nacisku lub uderzenia) nie pękają, dzięki czemu są użytecznym materiałem konstrukcyjnym. Temperatury topnienia metali są bardzo zróżnicowane. Rtęć jest cieczą w temperaturze pokojowej, a metale alkaliczne topią się poniżej 200°C. Kilka metali po przejściowych ma również niskie temperatury topnienia, podczas gdy metale przejściowe topią się w temperaturach powyżej 1000 ° C. Różnice te odzwierciedlają różnice w sile wiązania metalicznego pomiędzy metalami.

Rodzaje wiązań chemicznych

Teorie wiązań chemicznych zostały zapoczątkowane przez amerykańskiego chemika Gilberta N. Lewisa. Opracował model zwany modelem Lewisa, aby wyjaśnić typ i ...

Education

JoVE Core

Chemia

Jeden

Chemical Bonding: Basic Concepts

Wiązania chemiczne: Podstawowe pojęcia

KEY TERMS AND CONCEPTS

Kluczowe terminy i pojęcia

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 Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

Physical Science

PS.PSc.2.1

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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

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

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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.

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Bonding Types: From Nonpolar Covalent to Ionic

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Radioactive Decay and Radiometric Dating

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Nuclear Fission

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Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

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Nuclear Transmutation

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Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

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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

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

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Molar Mass

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Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

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Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

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Ionization Energy

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PS.Chm.2.2

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Chemical Bonding and Bond Properties

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