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

Quando gli atomi si avvicinano l'uno all'altro, i loro nuclei si respingono, così come gli elettroni. Allo stesso tempo, gli elettroni di ciascun atomo sono attratti l'uno dal nucleo dell'altro e si organizzano in modo tale da massimizzare le forze attrattive tra gli atomi riducendo al minimo le forze repulsive.
Se ciò si traduce in una forza attrattiva netta, l'energia potenziale del sistema viene ridotta. Questa interazione è chiamata legame chimico.
Tuttavia, non tutte le combinazioni di atomi possono formare legami chimici stabili. Il comportamento chimico di un atomo è determinato principalmente da ciò che forma legami e dal tipo di legami che sono. Comprendere il legame tra gli atomi che compongono un composto aiuta a comprendere e prevedere il loro comportamento molecolare.
L'energia di legame è l'energia necessaria per rompere un legame in una mole di un composto gassoso. Dipende dal tipo di atomi legati e dal numero di elettroni coinvolti. La forza del legame aumenta con l'energia del legame.
Il tipo di atomi legati e il numero di elettroni coinvolti influenzano anche la lunghezza del legame, che è la distanza media tra i nuclei di due atomi legati ed è inversamente proporzionale alla molteplicità del legame e alla forza del legame.
Le interazioni di legame più comuni rientrano in uno spettro che va dai legami ionici, che coinvolgono attrazioni elettrostatiche tra ioni di carica opposta, ai legami covalenti, che condividono elettroni di valenza tra gli atomi.
Il legame ionico è l'interazione primaria che si trova nei composti ionici. I cationi e gli anioni costituenti sono tenuti insieme da forze elettrostatiche di attrazione. Spesso, la formazione di ioni è preceduta dal trasferimento di elettroni di valenza tra gli atomi partecipanti.
L'atomo che perde elettroni diventa il catione, mentre l'atomo che accetta elettroni diventa l'anione. Il trasferimento di elettroni in genere dà a ciascuno ione la configurazione di gas nobile più vicina, che è la configurazione raggiunta con la più piccola variazione nel numero di elettroni, rendendo gli ioni energeticamente più stabili.
Nel legame covalente, gli elettroni condivisi interagiscono con i nuclei degli atomi di legame e riducono l'energia potenziale. I doppi e tripli legami condividono rispettivamente due e tre coppie di elettroni tra gli atomi. Poiché questo aumenta il numero di elettroni soggetti a forze attrattive aggiuntive dall'altro nucleo, la forza del legame aumenta con la molteplicità del legame.

legami chimici

Gli atomi partecipano alla formazione di legami chimici per acquisire una configurazione elettronica completa del guscio di valenza simile a quella del gas nobile più vicino in termini di numero atomico. I legami ionici, covalenti e metallici sono alcuni tipi importanti di legami chimici. L’energia e la lunghezza del legame determinano la forza di un legame chimico.

Tipi di legami chimici

Un legame ionico si forma a causa dell'attrazione elettrostatica tra cationi e anioni. Spesso gli ioni si formano mediante il trasferimento di elettroni da un atomo partecipante all'altro. Tuttavia, questi legami non hanno una direzionalità definita perché la forza di attrazione elettrostatica è distribuita uniformemente in tutto lo spazio tridimensionale.

Un legame covalente è un legame chimico formato dalla condivisione di coppie di elettroni tra atomi adiacenti. La coppia di elettroni condivisa è chiamata coppia di legame. I legami covalenti hanno natura direzionale.

Un legame metallico si forma tra due atomi di metallo. Il legame metallico è descritto dal “modello del mare di elettroni”. Basato sulle basse energie di ionizzazione dei metalli, il modello afferma che gli atomi metallici perdono facilmente i loro elettroni di valenza e diventano cationi. Questi elettroni di valenza creano un pool di elettroni delocalizzati che circondano i cationi sull'intero metallo.

Energie di legame e Lunghezza del legame

La forza di un legame covalente è misurata dall'energia necessaria per romperlo, cioè dall'energia necessaria per separare gli atomi legati. Separare qualsiasi coppia di atomi legati richiede energia. Più forte è un legame, maggiore è l’energia necessaria per romperlo.

L'energia richiesta per rompere uno specifico legame covalente in una mole di molecole gassose è chiamata energia di legame o energia di dissociazione del legame. L'energia di legame per una molecola biatomica è definita come la variazione di entalpia standard per la reazione endotermica. Le molecole con tre o più atomi hanno due o più legami. La somma di tutte le energie di legame in tale molecola è uguale alla variazione di entalpia standard per la reazione endotermica che rompe tutti i legami nella molecola.

La forza di un legame tra due atomi aumenta all’aumentare del numero di coppie di elettroni nel legame. In generale, maggiore è il numero di legami tra due atomi, minore è la lunghezza del legame e maggiore è la sua forza. Pertanto, i tripli legami sono più forti e più corti dei doppi legami tra gli stessi due atomi; allo stesso modo, i doppi legami sono più forti e più corti dei singoli legami tra gli stessi due atomi. Quando un atomo si lega a vari atomi di un gruppo, tipicamente la forza del legame diminuisce man mano che si scende nel gruppo.

Legami chimici


Gli atomi partecipano alla formazione di un legame chimico per acquisire una configurazione elettronica completa del guscio di valenza simile a quella del gas nobile più vicino ...

Education

Didattica

JoVE Core

Organic Chemistry

Chimica Organica

Unit 1

Unità 1

Covalent Bonding and Structure

Legame covalente e struttura

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

what is organic chemistry?

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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...

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electron configurations

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chemical bonds

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

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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

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molecular geometry and dipole moments

Predicting Shape and Molecular Polarity

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Covalent Bond Overlap and Orbital Hybridization

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mo theory and covalent bonding

Bond Order and Molecular Orbitals

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intermolecular forces and physical properties

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solubility

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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

Explore ionic, covalent, and metallic bonds, plus bond energy and bond length. Learn how bond type affects strength in high school chemistry.

Chemical Bonds: Types and Strength | JoVE K12

organic chemistry

JoVE Core Organic Chemistry spiega i concetti di base della stereochimica, delle reazioni e dei meccanismi usando video-lezioni concise e facili da capire. Inoltre, i video scientist-in-action dimostrano l'applicazione di tali concetti in esperimenti di ricerca classici e originali eseguiti al giorno d'oggi nei laboratori in tutto il mondo.

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HS-PS2-6

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Ohio’s Learning Standards and Model Curriculum

9-12

Physical Geology

Minerals

Chemical bonding (ionic, covalent, metallic)

Tennessee Academic Standards

Motion and Stability: Forces and Interactions

CHEM1.PS2.1

Virginia  Standards of Learning

HIgh School

Physics

PH.9

PH.9.e

Minnesota Academic Standards in Science

1.1.1 9L.4.2.1.1

3.1.1 9C.2.2.1.2

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South Carolina College and Career Ready Science Standards

Matter and Its Interactions

C-PS1-3.

C-PS2-6.

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HS-PS1-2

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HS-PS1-4

Chemical Bonds: Types and Strength

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