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

Während Oxidations-Reduktion- oder Redox-Reaktionen werden Elektronen zwischen Atomen übertragen.
 Das Molekül, das ein Elektron spendet, wird oxidiert und das Molekül, das ein Elektron empfängt, wird reduziert.
 Es hat eine weniger positive Ladung.
 Wenn beispielsweise neutrale Natrium- und Chloratome zu Ionen werden, verliert Natrium ein Elektron, oxidiert und Chlor gewinnt ein Elektron.
 Es wird reduziert.
 Darüber hinaus wird das Molekül, das ein Elektron spendet, als Reduktionsmittel bezeichnet, während das Molekül, das das Elektron empfängt, das Oxidationsmittel ist.
 Auch hier wird Natrium oxidiert, also ist es ein Reduktionsmittel, und Chlor wird reduziert, also ist es das Oxidationsmittel.

Flowers, P., Theopold, K., Langley, R., Robinson, W. R., Clark, M. A., Douglas, M., Choi, J. Abschnitt 4.2: Klassifizierung chemischer Reaktionen. In Chemie 2e. OpenStax. Houston, TX (2019).

redox-reaktionen

Oxidations-Reduktions- bzw. Redox-Reaktionen verändern die Oxidationszustände von Atomen durch den Transfer von Elektronen von einem Atom, dem Reduktionsmittel, zu einem Elektronen-aufnehmendem Atom, was auch Oxidationsmittel genannt. Dabei oxidiert das Atom, welches seine Elektronen abgibt, und das Atom, welches Elektronen aufnimmt, wird reduziert, da es eine nun weniger positive Ladung durch die Elektronenaufnahme hat. Der Transfer der Energie in Redox-Reaktionen ist von dem Potential der Atome Bindungselektronen anzuziehen abhängig. Dies bezeichnet man als Elektronegativität. Ist das Oxidationsmittel stärker elektronegativ als das Reduktionsmittel, so wird Energie freigesetzt. Ist jedoch das Oxidationsmittel weniger elektronegativ als das Reduktionsmittel, ist eine Zugabe von Energie erforderlich.
 
 <h4>Reduktionsmittel werden oxidiert</h4>
 
 Ist die Oxidation ein Verlust oder Gewinn von Elektronen? Die Terminologie kann hier recht verwirrend sein. Das englische Akronym OIL RIG kann zur Erinnerung verwendet werden. Es steht für Oxidation Ist verLust; Reduktion Ist Gewinn. Wenn ein Atom also oxidiert wird, verliert es Elektronen. Als Reduktionsmittel überträgt das oxidierte Atom Elektronen auf ein anderes Atom, wodurch es reduziert wird. Mit OIL RIG im Hinterkopf können die meisten Fragen zu den Mitgliedern einer Redox-Reaktion beantwortet werden.
 
 <h4>Elektronegativität und Energie</h4>
 
 Redox-Reaktionen benötigen oder erzeugen Energie. Verliert ein Atom ein Elektron an ein elektronegativeres Atom, dann ist es eine energetisch günstige Reaktion und Energie wird freigesetzt. Das ist eigentlich sehr logisch. Ähnlich wie ein starker Mann ein Tauziehen mit einem schwächeren Mann gewinnt, hat auch ein elektronegativeres Atom eine größere Kapazität Elektronen an sich zu ziehen. Ein biologisches Beispiel für diese Art von Reaktion ist die Zellatmung, bei der Energie freigesetzt und zur Erzeugung von ATP verwendet wird. ATP ist ein Energieträger, den Zellen leicht nutzen können.
 
 Andere Redox-Reaktionen benötigen Energie, anstatt diese freizusetzen. Bewegt sich ein Elektron von einem elektronegativeren Atom zu einem weniger elektronegativen Atom, muss Energie eingesetzt werden. Das ist dann so, als ob ein schwächerer Mann das Tauziehen mit einem stärkeren Mann gewinnen würde. Er würde auch Energie von einer externen Quelle benötigen. Ein biologisches Beispiel ist die Fotosynthese bei der Elektronen mit Hilfe von Energie in Form von Licht von Wasser auf Kohlendioxid übertragen werden.
 
 <h4>Unvollständige Übertragung von Elektronen</h4>
 
 Eine Redox-Reaktion kann nicht nur bei der Übertragung eines Elektrons auftreten, sondern auch bei einer Veränderung in der Elektronenaufteilung in einer Kovalenzbindung! Wenn z.B. Methan und Sauerstoff reagieren, entstehen Kohlenstoffdioxid und Wasser. In diesem Fall wird der Kohlenstoff im Methan oxidiert. Dies liegt daran, dass die Elektronen im Methan zu gleichen Teilen zwischen dem Kohlenstoff und dem Wasserstoff aufgeteilt sind, während der Kohlenstoff im Kohlendioxid ist teilweise positive Ladung hat, da der Sauerstoff die Elektronen stärker anzieht als der Kohlenstoff.

Redox-Reaktionen

Oxidations-Reduktions- oder Redoxreaktionen beinhalten die Übertragung von Elektronen von einem Molekül oder Atom auf ein anderes. Wenn ein Atom ein Elektron gewinnt, wird ein anderes ...

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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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hydrogen bonds

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van der waals interactions

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redox reactions

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cohesion

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adhesion

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solvents

Water as a Biological Solvent

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carbon skeletons

Carbon Backbones in Biomolecules

Carbon backbones give biological molecules their structure and flexibility. Living things are built from macromolecules that contain carbon atoms, and organic compounds are defined by a carbon backbone. Carbon is tetravalent, so each carbon atom can bond with four other atoms. Its valence electrons are stable, so carbon rarely becomes an ion. As carbon chains get longer, they can form ring structures, double bonds, and branching side chains. Carbon-carbon bonds create the carbon skeleton.

key terms and concepts

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

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Electron Transfer in Redox

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