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 os átomos se aproximam, seus núcleos se repelem, assim como os elétrons. Ao mesmo tempo, os elétrons de cada átomo são atraídos para o núcleo um do outro e se organizam de forma a maximizar as forças atrativas entre os átomos, minimizando as forças repulsivas.
Se isso resultar em uma força atrativa líquida, a energia potencial do sistema é reduzida. Essa interação é chamada de ligação química.
No entanto, nem toda combinação de átomos pode formar ligações químicas estáveis. O comportamento químico de um átomo é determinado principalmente pelo que forma ligações e que tipo de ligações são. Compreender a ligação entre os átomos que formam um composto ajuda a compreender e prever seu comportamento molecular.
A energia de ligação é a energia necessária para quebrar uma ligação em um mol de um composto gasoso. Depende do tipo de átomos ligados e do número de elétrons envolvidos. A força de ligação aumenta com a energia de ligação.
O tipo de átomos ligados e o número de elétrons envolvidos também influenciam o comprimento da ligação, que é a distância média entre os núcleos de dois átomos ligados e é inversamente proporcional à multiplicidade da ligação e à força da ligação.
As interações de ligação mais comuns caem em um espectro que varia de ligações iônicas, que envolvem atrações eletrostáticas entre íons de cargas opostas, a ligações covalentes, que compartilham elétrons de valência entre átomos.
A ligação iônica é a principal interação encontrada em compostos iônicos. Os cátions e ânions constituintes são mantidos juntos por forças eletrostáticas de atração. Freqüentemente, a formação de íons é precedida pela transferência de elétrons de valência entre os átomos participantes.
O átomo que perde elétrons torna-se o cátion, enquanto o átomo que aceita elétrons torna-se o ânion. A transferência de elétrons normalmente dá a cada íon a configuração de gás nobre mais próxima, que é a configuração alcançada com a menor mudança no número de elétrons, tornando os íons energeticamente mais estáveis.
Na ligação covalente, os elétrons compartilhados interagem com os núcleos dos átomos de ligação e diminuem a energia potencial. As ligações duplas e triplas compartilham dois e três pares de elétrons entre os átomos, respectivamente. À medida que isso aumenta o número de elétrons sujeitos a forças atrativas adicionais do outro núcleo, a força de ligação aumenta com a multiplicidade de ligações.

ligações químicas

Átomos participam da formação de ligação química para adquirir uma configuração eletrônica completa da camada de valência, semelhante à do gás nobre mais próximo dele em número atômico. Ligações iônicas, covalentes e metálicas são alguns dos tipos importantes de ligações químicas. A energia e o comprimento da ligação determinam a força de uma ligação química.

Tipos de ligações químicas

Uma ligação iônica é formada devido à atração eletrostática entre cátions e ânions. Frequentemente, os íons são formados pela transferência de elétrons de um átomo participante para outro. Porém, essas ligações não possuem uma direcionalidade definida porque a força eletrostática de atração é distribuída uniformemente por todo o espaço tridimensional.

Uma ligação covalente é uma ligação química formada pelo compartilhamento de pares de elétrons entre átomos adjacentes. O par de elétrons compartilhado é chamado de par de ligação. As ligações covalentes são de natureza direcional.

Uma ligação metálica é formada entre dois átomos de metal. A ligação metálica é descrita pelo modelo de “Mar de Elétrons”. Com base nas baixas energias de ionização dos metais, o modelo afirma que os átomos metálicos perdem facilmente seus elétrons de valência e se tornam cátions. Esses elétrons de valência criam um conjunto de elétrons deslocalizados ao redor dos cátions por todo o metal.

Energias de ligação e comprimento de ligação

A força de uma ligação covalente é medida pela energia necessária para quebrá-la, isto é, a energia necessária para separar os átomos ligados. Separar qualquer par de átomos ligados requer energia. Quanto mais forte for uma ligação, maior será a energia necessária para quebrá-la.

A energia necessária para quebrar uma ligação covalente específica em um mol de moléculas gasosas é chamada de energia de ligação ou energia de dissociação de ligação. A energia de ligação para uma molécula diatômica é definida como a mudança de entalpia padrão para a reação endotérmica. Moléculas com três ou mais átomos possuem duas ou mais ligações. A soma de todas as energias de ligação em tal molécula é igual à variação de entalpia padrão para a reação endotérmica que quebra todas as ligações na molécula.

A força de uma ligação entre dois átomos aumenta à medida que o número de pares de elétrons na ligação aumenta. Geralmente, quanto maior o número de ligações entre dois átomos, menor será o comprimento da ligação e maior será a força da ligação. Assim, as ligações triplas são mais fortes e mais curtas do que as ligações duplas entre os mesmos dois átomos; da mesma forma, as ligações duplas são mais fortes e mais curtas do que as ligações simples entre os mesmos dois átomos. Quando um átomo se liga a vários átomos de um grupo, a força da ligação normalmente diminui à medida que descemos no grupo.

Esse texto foi adaptado do <a href="https://openstax.org/books/chemistry-2e/pages/7-1-ionic-bonding">Openstax, Chemistry 2e, Section 7.1: Ionic Bonding</a>, <a href="https://openstax.org/books/chemistry-2e/pages/7-2-covalent-bonding">Openstax, Section 7.2: Covalent Bonding</a>, <a href="https://openstax.org/books/chemistry-2e/pages/10-5-the-solid-state-of-matter">Section 10.5: The Solid State of Matter</a>, and Section<a href="https://openstax.org/books/chemistry-2e/pages/7-5-strengths-of-ionic-and-covalent-bonds"> 7.5. Bond Strength: Covalent Bonds</a>.

Ligações químicas


Os átomos participam de uma formação de ligação química para adquirir uma configuração eletrônica completa da camada de valência semelhante à do gás nobre mais próximo ...

Education

JoVE Core

Organic Chemistry

Química Orgânica

Unit 1

Unidade 1

Covalent Bonding and Structure

Ligação Covalente e Estrutura

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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

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chemical bonds

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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...

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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

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Minerals

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Physics

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HS-PS1-4

Chemical Bonds: Types and Strength

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