Name: how atoms bond to reach stability
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 1 s
Channel: JoVE

Les liaisons chimiques maintiennent les atomes d’une molécule ou d’un composé ensemble. Les liaisons se forment lorsque les électrons de la couche de valence de l'atome sont donnés ou partagés avec d'autres atomes.
Par exemple, les liaisons ioniques se forment lorsque les atomes donnent ou acceptent des électrons, remplissant leur couche de valence. Un atome qui donne des électrons et devient chargé positivement est un cation, tandis qu’un atome qui accepte des électrons et devient chargé négativement est un anion.
Dans le sel de table, l’association entre le cation sodium et l’anion chlorure est une liaison ionique.
Les liaisons covalentes se forment entre des atomes qui partagent mutuellement une ou plusieurs paires d’électrons de valence.
Par exemple, deux atomes d’hydrogène peuvent partager une paire d’électrons, formant une seule liaison covalente. L’oxygène et l’azote peuvent partager deux et trois paires d’électrons, formant des liaisons doubles et triples.

introduction aux liaisons chimiques

Introduction to Chemical Bonds

Liaisons chimiques Les électrons de la couche énergétique la plus externe déterminent la stabilité énergétique de l'atome et sa tendance à former des liaisons chimiques avec d'autres atomes. La couche électronique la plus interne a une capacité maximale de deux électrons, mais les deux couches électroniques suivantes peuvent chacune avoir un maximum de huit électrons. C'est ce qu'on appelle la règle de l'octet, qui stipule que, à l'exception de la couche la plus interne, les atomes sont plus stables énergiquement lorsqu'ils ont huit électrons dans leur couche de valence, la couche électronique la plus externe. Cependant, comme tous les éléments n'ont pas suffisamment d'électrons pour remplir leurs couches les plus externes, les atomes forment des liaisons chimiques avec d'autres atomes, obtenant ainsi les électrons dont ils ont besoin pour atteindre une configuration électronique stable. Par conséquent, une liaison chimique est la force qui maintient les atomes ensemble dans une molécule ou un composé. Liaisons ioniques Les atomes peuvent gagner ou perdre des électrons pour remplir leur couche de valence. Ce faisant, ils deviennent chargés électriquement et sont appelés ions. Un cation est un atome chargé positivement qui perd des électrons, tandis qu'un atome qui gagne des électrons et devient chargé négativement est un anion. Les charges opposées des cations et des anions exercent une attraction mutuelle modérément forte qui maintient les atomes à proximité, formant une liaison ionique. Une liaison ionique est une association étroite et continue entre des ions de charges opposées. Le sel de table commun doit son existence à la liaison ionique. Liaisons covalentes Une autre façon de satisfaire la règle de l'octet est le partage d'électrons entre les atomes pour former des liaisons covalentes. Ces liaisons sont plus fortes et beaucoup plus courantes que les liaisons ioniques dans les molécules des organismes vivants. Les liaisons covalentes se trouvent couramment dans les molécules organiques à base de carbone, telles que notre ADN et nos protéines. Les liaisons covalentes se trouvent également dans les molécules inorganiques telles que l'eau, le dioxyde de carbone et l'oxygène. Liaisons hydrogène Une liaison hydrogène se forme lorsqu'un atome d'hydrogène faiblement positif déjà lié à un autre atome électronégatif (par exemple, l'oxygène dans la molécule d'eau) est attiré par un autre atome électronégatif d'une molécule différente. L'exemple le plus courant de liaison hydrogène dans le monde naturel se produit entre les molécules d'eau. Cela se produit chaque fois que deux gouttes de pluie se rejoignent pour former une plus grosse goutte ou qu'un ruisseau se déverse dans une rivière. La liaison hydrogène se produit parce que l'atome d'oxygène faiblement négatif dans une molécule d'eau est attiré par les atomes d'hydrogène faiblement positifs de deux autres molécules d'eau. Ce texte est partiellement adapté de <a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/2-2-chemical-bonds?query=chemical%20bond&target=%7B%22type%22%3A%22search%22%2C%22index%22%3A0%7D#fs-id1493624">Openstax, Anatomy and Physiology 2e, Section 2.2: Chemical Bonds.</a> <a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds">Openstax, </a><a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds">Biology for AP® Courses</a><a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds"> Section </a><a href="https://openstax.org/books/biology-ap-courses/pages/2-1-atoms-isotopes-ions-and-molecules-the-building-blocks?query=chemical%20bonds">2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks.</a>

Introduction aux liaisons chimiques

Liaisons chimiques
Les électrons du niveau d’énergie le plus externe déterminent la stabilité énergétique de l’atome et sa tendance à former des liaisons chimiques avec ...

Education

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JoVE Core

Anatomy and Physiology

Anatomie et physiologie

Unit 1

Unité 1

Fundamentals of Chemistry

Les fondamentaux de la chimie

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

how atoms bond to reach stability

Atoms bond to become more stable, and their outermost electrons play the biggest role in that process. The inner electron shell can hold two electrons. The next two shells can each hold eight electrons. This is called the octet rule. It states that, except for the innermost shell, atoms are most stable when their valence shell, or outer shell, has eight electrons.

When atoms do not have enough electrons to fill that outer shell, they form chemical bonds with other atoms. A chemical bond is the force that holds atoms together in a molecule or compound. These bonds let atoms reach a more stable electron arrangement.

One common type is an ionic bond. In this case, atoms gain or lose electrons to fill their valence shell. When they do this, they become ions. A cation is a positively charged ion that has lost electrons. An anion is a negatively charged ion that has gained electrons. The opposite charges attract each other and keep the ions close together. This close association forms an ionic bond. Table salt is a common example of a substance made through ionic bonding.

Another way atoms satisfy the octet rule is by sharing electrons. This creates covalent bonds. Covalent bonds are stronger and much more common than ionic bonds in the molecules of living organisms. They are found in carbon-based organic molecules such as DNA and proteins. They also occur in inorganic molecules like water, carbon dioxide, and oxygen.

Hydrogen bonds are a weaker kind of attraction. They form when a weakly positive hydrogen atom, already bonded to another electronegative atom such as oxygen, is attracted to a different electronegative atom in another molecule. Water is the most common example. Hydrogen bonding helps explain why raindrops can merge into larger beads and why a creek can flow into a river.

How Atoms Bond to Reach Stability

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introduction to chemical bonds

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ionic bonds

Ionic Bonds and Charge Transfer

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covalent bonds

Polar and Nonpolar Covalent Bonds

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hydrogen bonds

Hydrogen Bonding and DNA Stability

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key terms and concepts

Learn how atoms use ionic, covalent, and hydrogen bonds to reach stability. Explore valence electrons, ions, and examples like salt and water.

How Atoms Bond to Reach Stability | JoVE K12

anatomy and physiology

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How Atoms Bond to Reach Stability

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