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

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Earth and Environmental Science

Earth's Systems

ESS.EES.3.1

Redox Reactions

Certain processes that are vital to life, including photosynthesis, combustion, and corrosion, fall into the class of reactions called oxidation&#8211;reduction, or redox, reactions.
Redox reactions consist of two simultaneous processes: oxidation and reduction.
Oxidation and reduction are complementary processes. In a redox reaction between two reactants, one reactant loses electrons and is oxidized, while the other reactant gains electrons and is reduced.
Consider the oxidation&#8211;reduction reaction between potassium and chlorine.
The neutral potassium atom loses an electron to become a potassium ion. Potassium is oxidized, and its charge increases from zero in the neutral atom to one-plus in the cation.
The neutral chlorine atom gains an electron and becomes a chloride ion. Chlorine is reduced, and its charge decreases from zero in the neutral atom to one-minus in the anion.
Since potassium donates an electron, it is the reducing agent, or reductant. Chlorine accepts the electron, so it is the oxidizing agent, or an oxidant. The redox process leads to the formation of potassium chloride.

redox reactions

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another atom must lose an electron, meaning oxidation and reduction must occur together. Since the redox occurs in pairs, the atom that gets oxidized is also called the reducing agent or reductant, and the atom that is reduced is also called the oxidizing agent or oxidant. A straightforward way to remember the definitions of oxidation and reduction is through the phrase OIL-RIG, which stands for: Oxidation Is Losing&#8211; Reduction Is Gaining (electrons). 
 
Oxidation states
A redox reaction changes the atom's oxidation states. The oxidation state or number refers to the charge an atom would have if each of its bonds to other elements were purely ionic. Determining whether there are changes in the oxidation numbers of atoms in one or more reactants can help determine whether a reaction is an oxidation-reduction reaction.
In the reaction between sodium and chlorine to yield sodium chloride, sodium becomes oxidized, and chlorine becomes reduced,
<img alt="Chemical reaction formula: sodium and chlorine forming sodium chloride, solid-gas reaction, equation." src="/files/ftp_upload/10671/Equation_1.svg" style="text-align: center; height: 13px;" data-altupdatedat="1761830439000" data-alt="Equation1" />
It is helpful to view the process that happens to each reactant separately, that is, to represent the fate of each reactant in the form of an equation called a half-reaction:
<img alt="Sodium oxidation equation, 2Na(s) &#8594; 2Na&#8314;(s) + 2e&#8315;, redox process, chemistry formula." src="/files/ftp_upload/10671/Equation_2.svg" style="text-align: center; height: 13px;" data-altupdatedat="1761830439000" data-alt="Equation2" />
<img alt="Redox reaction equation showing chlorine gas reduction to chloride ion; chemical transformation." src="/files/ftp_upload/10671/Equation_3.svg" style="text-align: center; height: 13px;" data-altupdatedat="1761830439000" data-alt="Equation3" />
These equations show that Na atoms lose electrons, going from an oxidation number of 0 to 1+, while Cl atoms (in the Cl2 molecule) gain electrons, going from an oxidation number of 0 to 1-.
Incomplete Transfer of Electrons
A redox reaction can occur not only when an electron gets transferred but also when there is a change in the sharing of the electrons in a covalent bond. For example, methane and oxygen can react to form carbon dioxide and water. The electrons in methane are shared equally between carbon and hydrogen, but carbon dioxide's carbon is partially positive since oxygen attracts electrons more than carbon. Carbon dioxide is losing electrons, becoming oxidized, and oxygen is gaining electrons, becoming reduced.
This text is adapted from <a href="https://openstax.org/books/chemistry-2e/pages/4-2-classifying-chemical-reactions">Openstax, Chemistry 2e, Section 4.2: Classifying Chemical Reactions.</a>

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another ...

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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

Periodic Table Basics for Living Things

The periodic table helps explain which elements living things need and how those elements are related. Elements are the smallest units of matter that cannot be broken down further by chemical processes. There are 118 known elements, but not all occur naturally, and even fewer are essential for life. Living matter is made mostly of carbon, nitrogen, hydrogen, and oxygen. Together, these elements make up most of the human body and are also found in all life on Earth. Smaller amounts of calcium,...

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Ionic Compounds and Electrolytes

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chemical reactions

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Chemical reactions rearrange atoms to form new substances. In a reaction, the starting materials are called reactants, and the new substances are called products. The atoms stay the same type and number, but their bonds change, so the substances become different compounds. During a chemical reaction, bonds between atoms break and form again. This means the shared electrons are rearranged. Some reactions happen on their own, while others need an energy source such as heat or light. In biology,...

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

Water Molecules and Surface Tension

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adhesion

Water Climbing by Adhesion

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states of water

Water Phase Changes and Ice Density

Water changes between solid, liquid, and gas states as temperature and molecular motion change. In this lesson, the focus is on how water freezes, melts, vaporizes, and returns to liquid or solid form. The balance between intermolecular forces, which pull molecules together, and kinetic energy, which pushes them apart, controls each state. Water freezes when intermolecular forces become stronger than kinetic energy. Unlike most substances, ice is less dense than liquid water. This happens...

specific heat

How Specific Heat Affects Temperature

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vaporization

Vaporization, Boiling, and Evaporation

Vaporization changes a liquid into vapor when temperature adds enough kinetic energy to overcome intermolecular forces. It is a surface phenomenon, which means it starts at the liquid’s surface. The energy needed to vaporize a set amount of liquid at a given pressure and constant temperature is called the heat of vaporization. Water shows this process clearly. When liquid water is vaporized, it becomes steam. One way this happens is boiling, which occurs when vapor bubbles form beneath the...

solvents

Water as a Biological Solvent

Water acts as a biological solvent in many living systems. A solvent is a substance, usually a liquid, that dissolves another substance called a solute. When a solvent and a solute mix, they form a solution, which is a uniform mixture of both parts. Water is called a universal biological solvent because its polar structure helps it dissolve many other polar compounds. Polarity means that one side of the molecule has a slight positive charge and the other side has a slight negative charge.

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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