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

As ligações químicas mantêm os átomos de uma molécula ou composto juntos. As ligações se formam quando os elétrons na camada de valência do átomo são doados ou compartilhados com outros átomos.
Por exemplo, as ligações iônicas se formam quando os átomos doam ou aceitam elétrons, preenchendo sua camada de valência. Um átomo que doa elétrons e se torna carregado positivamente é um cátion, enquanto um que aceita elétrons e se torna carregado negativamente é um ânion.
No sal de cozinha, a associação entre o cátion sódio e o ânion cloreto é uma ligação iônica.
As ligações covalentes são formadas entre átomos que compartilham mutuamente um ou mais pares de elétrons de valência.
Por exemplo, dois átomos de hidrogênio podem compartilhar um par de elétrons, formando uma única ligação covalente. O oxigênio e o nitrogênio podem compartilhar dois e três pares de elétrons, formando ligações duplas e triplas.

introdução às ligações químicas

Introduction to Chemical Bonds

Ligações químicas

Os elétrons do nível de energia mais externo determinam a estabilidade energética do átomo, assim como sua tendência a formar ligações químicas com outros átomos. A camada eletrônica mais interna tem uma capacidade máxima de dois elétrons, mas as duas camadas eletrônicas seguintes podem ter um máximo de oito elétrons cada. Isso é conhecido como regra do octeto, que afirma que, com exceção da camada mais interna, os átomos são mais estáveis energeticamente quando têm oito elétrons em sua camada de valência, a camada eletrônica mais externa.

No entanto, como nem todos os elementos possuem elétrons suficientes para preencher suas camadas mais externas, os átomos formam ligações químicas com outros átomos, obtendo assim os elétrons necessários para ter uma configuração eletrônica estável. Portanto, uma ligação química é a força que mantém os átomos unidos em uma molécula ou composto.

Ligações iônicas

Os átomos podem ganhar ou perder elétrons para preencher sua camada de valência. Ao fazer isso, eles se tornam eletricamente carregados e são chamados de íons. Um cátion é um átomo com carga positiva que perdeu elétrons, enquanto um átomo que ganha elétrons e se torna carregado negativamente é um ânion. As cargas opostas de cátions e ânions exercem uma atração mútua moderadamente forte que mantém os átomos próximos, formando uma ligação iônica. Uma ligação iônica é uma associação contínua e próxima entre íons de carga oposta. O sal de cozinha comum deve sua existência a uma ligação iônica.

Ligações covalentes

Outra maneira de satisfazer a regra do octeto é compartilhando elétrons entre átomos para formar ligações covalentes. Essas ligações são mais fortes e muito mais comuns do que as ligações iônicas nas moléculas de organismos vivos. As ligações covalentes são frequentemente encontradas em moléculas orgânicas à base de carbono, como nosso DNA e proteínas. As ligações covalentes também são encontradas em moléculas inorgânicas como água, dióxido de carbono e oxigênio.

Ligações de hidrogênio

Uma ligação de hidrogênio é formada quando um átomo de hidrogênio fracamente positivo, já ligado a um átomo eletronegativo (por exemplo, o oxigênio na molécula de água), é atraído por outro átomo eletronegativo de outra molécula. O exemplo mais comum de ligação de hidrogênio no mundo natural ocorre entre moléculas de água. Ela acontece sempre que duas gotas de chuva se juntam para formar uma gota maior, ou quando um riacho deságua em um rio maior. A ligação de hidrogênio ocorre porque o átomo de oxigênio fracamente negativo em uma molécula de água é atraído pelos átomos de hidrogênio fracamente positivos de outras duas moléculas de água.

Este texto foi parcialmente adaptado 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>

Introdução às ligações químicas

Ligações Químicas
Os elétrons do nível de energia mais externo determinam a estabilidade energética do átomo e sua tendência a formar ligações químicas com ...

Education

JoVE Core

Anatomy and Physiology

Anatomia e Fisiologia

Unit 1

Unidade 1

Fundamentals of Chemistry

Fundamentos da Química

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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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How Atoms Bond to Reach Stability

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