Name: electron transfer in redox
Uploaded: 2019-03-11T09:21:00.000Z
Duration: 1 min 24 s
Channel: JoVE

K12 Standards

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North Carolina K-12 Science Standard Course of Study

9-12

Earth and Environmental Science

Earth's Systems

ESS.EES.3.1

Redox Reactions

Durante as reações de oxidação-redução, ou reações redox, eletrões são transferidos entre átomos. A molécula que doa um eletrão é oxidada. E a molécula que recebe um eletrão é reduzida.Tem uma carga menos positiva. Por exemplo, quando átomos neutros de sódio e cloro tornam-se íons, o sódio perde um eletrão, sendo oxidado, e o cloro ganha um eletrão, sendo reduzido. Além disso, a molécula que doa um eletrão é chamada de agente redutor.Considerando que a molécula que recebe o eletrão é o agente oxidante. Novamente, o sódio é oxidado, então é o agente redutor. E o cloro é reduzido, então é o agente oxidante.

Flowers, P., Theopold, K., Langley, R., Robinson, W. R., Clark, M. A., Douglas, M., Choi, J. Seção 4.2: Classificação de Reações Químicas. Em Química 2e. OpenStax. Houston, TX (2019).

reações redox

Reações de oxidação-redução, ou redox, alteram os estados de oxidação dos átomos através da transferência de eletrões de um átomo, o agente redutor, para outro átomo que recebe o eletrão, o agente oxidante. Aqui, o átomo que doa eletrões é oxidado—perde eletrões—e o átomo que aceita eletrões é reduzido—tem uma carga menos positiva porque ganha eletrões. O movimento da energia nas reações redox depende do potencial dos átomos para atrair eletrões para ligação—a sua eletronegatividade. Se o agente oxidante for mais eletronegativo do que o agente redutor, então a energia é libertada. No entanto, se o agente oxidante for menos eletronegativo do que o agente redutor, é necessário que entre energia.
 
 <h4>Agentes Reduzidos São Oxidados</h4>
 
 A oxidação é uma perda ou ganho de eletrões? A terminologia pode ser confusa. O acrónimo OIL RIG é comumente usado para lembrar. Significa oxidação é perda; redução é ganho. Então, se um átomo é oxidado, perde eletrões. Como agente redutor, o átomo oxidado transfere eletrões para outro átomo, fazendo com que ele seja reduzido. Com OIL RIG em mente, a maioria das perguntas sobre os membros de uma reação redox pode ser respondida.
 
 <h4>Electronegatividade e Energia</h4>
 
 Reações redox produzem ou requerem energia. Se um átomo perde um eletrão para um átomo mais eletronegativo, então é uma reação energeticamente favorável, e a energia é libertada. Isto é na verdade muito lógico—semelhante a um homem forte a ganhar o jogo da corda com um homem mais fraco—porque um átomo mais eletronegativo tem uma maior capacidade de puxar eletrões para si mesmo. Um exemplo biológico desse tipo de reação é a respiração celular, na qual energia é libertada e usada para criar ATP, um tipo de energia que as células podem facilmente usar.
 
 Outras reações redox requerem energia, em vez de a libertarem. Se um eletrão passa de um átomo mais eletronegativo para um átomo menos eletronegativo, é preciso usar energia. Isto é como um homem mais fraco a ganhar o jogo da corda com um homem mais forte—requer energia de uma fonte externa. Um exemplo biológico é a fotossíntese, na qual os eletrões são transferidos da água para o dióxido de carbono com a ajuda de energia em forma de luz.
 
 <h4>Transferência Incompleta de Eletrões</h4>
 
 Uma reação de redox pode ocorrer não só quando um eletrão é transferido, mas também quando há uma alteração no compartilhamento de um eletrão em uma ligação covalente! Por exemplo, quando o metano e o oxigénio reagem, produzem dióxido de carbono e água. Neste caso, o carbono do metano é oxidado. Isso ocorre porque os eletrões do metano são compartilhados igualmente entre o carbono e o hidrogénio, enquanto que o carbono no dióxido de carbono é parcialmente positivo, uma vez que o oxigénio atrai eletrões mais do que o carbono.

Reações Redox

As reações de oxidação-redução ou redox envolvem a transferência de elétrons de uma molécula ou átomo para outro. Quando um átomo ganha um elétron, outro ...

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electron transfer in redox

Redox reactions are chemical reactions that involve electron transfer between atoms or molecules. When one particle gains electrons, another must lose them at the same time. That is why oxidation and reduction always happen together.

The two roles in a redox reaction are linked. The atom that is oxidized acts as the reducing agent, or reductant. The atom that is reduced acts as the oxidizing agent, or oxidant. A simple way to remember the ideas is OIL-RIG, which means oxidation is losing electrons and reduction is gaining electrons.

Redox reactions also change oxidation states, or oxidation numbers. An oxidation state is the charge an atom would have if all of its bonds were purely ionic. Checking whether oxidation numbers change in the reactants can help identify a redox reaction.

A sodium and chlorine reaction makes this idea clear. Sodium is oxidized, and chlorine is reduced to form sodium chloride. The process can be shown with half-reactions, which separate the fate of each reactant. In these equations, sodium goes from an oxidation number of 0 to 1+, while chlorine in Cl2 goes from 0 to 1-.

Electron transfer is not always complete. A redox reaction can also happen when the sharing of electrons changes in a covalent bond. Methane and oxygen can react to form carbon dioxide and water. In methane, electrons are shared equally between carbon and hydrogen, but in carbon dioxide the carbon is partially positive because oxygen pulls electrons more strongly. In that reaction, carbon dioxide is oxidized and oxygen is reduced.

Electron Transfer in Redox

the periodic table and organismal elements

the-periodic-table-and-organismal-elements

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covalent bonds

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ionic bonds

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hydrogen bonds

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van der waals interactions

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redox reactions

Redox reactions are chemical reactions that involve electron transfer between atoms or molecules. When one particle gains electrons, another must lose them at the same time. That is why oxidation and reduction always happen together. The two roles in a redox reaction are linked. The atom that is oxidized acts as the reducing agent, or reductant. The atom that is reduced acts as the oxidizing agent, or oxidant. A simple way to remember the ideas is OIL-RIG, which means oxidation is losing...

cohesion

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adhesion

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states of water

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vaporization

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solvents

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carbon skeletons

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key terms and concepts

Learn how redox reactions move electrons, change oxidation states, and use half-reactions to track sodium, chlorine, methane, and oxygen.

Electron Transfer in Redox | JoVE K12

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Electron Transfer in Redox

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