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

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Earth and Environmental Science

Earth's Systems

ESS.EES.3.1

Redox Reactions

在氧化还原反应中
 
 电子在两个原子之间进行交换
 
 贡献电子的分子是被氧化的
 
 接受电子的分子是被还原的
 
 它就有一个少量的正电
 
 打个比方，当一个中性的钠原子和氯原子
 
 成为了离子，钠就失去了一个电子
 
 它就被氧化了；而氯获得了一个原子，它就被还原了
 
 而且，贡献电子的分子就叫做
 
 还原剂
 
 而接受电子的分子就叫做
 
 氧化剂
 
 重复一遍，钠是被氧化的，所以是还原剂
 
 氯是被还原的，所以是氧化剂

Flowers， P.， Theopold， K.， Langley， R.， Robinson， WR， Clark， MA， Douglas， M.， Choi， J. 第 4.2 节:化学反应分类。在化学 2e.OpenStax 的。德克萨斯州休斯顿（2019 年）。

氧化还原反应

氧化还原反应通过电子从一个原子（还原剂）转移到另一个接受电子（氧化剂）的原子，从而改变原子的氧化状态。在这里，提供电子的原子被氧化了——它失去了电子——而接受电子的原子被还原了——它带的正电荷更少，因为它得到了电子。氧化还原反应中能量的运动依赖于原子吸引成键电子（它们的电负性）的势能。如果氧化剂的电负性大于还原剂，则释放能量。但是，如果氧化剂的电负性低于还原剂，则需要输入能量。

<h4>还原剂氧化</h4>
 
氧化是电子的损失还是增加？术语可能会让人混淆。OIL RIG的缩写词通常被用来记忆。代表氧化就是损失，还原就是收益。所以，如果一个原子被氧化，它就会失去电子。作为还原剂，被氧化的原子将电子转移到另一个原子上，使其还原。牢记OIL RIG，大多数关于氧化还原反应的问题都可以得到解答。
 
<h4>电负性与能量</h4>
 
氧化还原反应产生或需要能量。如果一个原子把一个电子输给一个电负性更强的原子，那么它就是一个能量有利的反应，能量被释放。这实际上是非常合乎逻辑的，类似于一个强壮的人赢得了与一个虚弱的人的拔河比赛，因为一个电负性更强的原子有更大的能力将电子拉向自己。这种反应的一个生物学例子是细胞呼吸，在这种呼吸中能量被释放并被用来产生三磷酸腺苷（ATP），ATP是一种细胞很容易利用的能量形式。
 
其它氧化还原反应需要能量，而不是释放能量。如果一个电子从一个电负性较强的原子移动到一个电负性较弱的原子，就必须使用能量。这就像一个弱者赢得了与一个强者的拔河比赛，它需要来自外部的能量。一个生物学的例子是光合作用，在光的形式的能量的帮助下，电子从水转移到二氧化碳。
 
<h4>电子不完全转移</h4>
 
氧化还原反应不仅在电子转移时发生，而且在共价键中电子的共享发生变化时也会发生！例如，当甲烷和氧气发生反应时，它们产生二氧化碳和水。在这种情况下，甲烷中的碳被氧化。这是因为甲烷中的电子在碳和氢之间平均分配，而二氧化碳中的碳是部分正的，因为氧比碳更吸引电子。

氧化还原反应涉及电子从一个分子或原子向另一个分子或原子的转移。当一个原子获得一个电子时，另一个……

Education

教育

JoVE Core

Biology

生物学

Fundamentals

基础知识

Chemistry of Life

生命化学

KEY TERMS AND CONCEPTS

关键术语与概念

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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Atoms are the smallest units of elements, and they make up all matter. Each atom contains three subatomic particles: protons, neutrons, and electrons. These particles give an atom its mass and its charge. The idea that matter is made of tiny particles goes back to Democritus, a Greek philosopher around 450 B.C. He used the word atomos, which means “indivisible.” The idea was not accepted at the time, but it returned many centuries later. In the 19th century, John Dalton proposed an atomic...

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electron orbital model

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covalent bonds

Electronegativity and Covalent Bond Polarity

Covalent bonds form when two atoms share electrons to fill their valence shells. The way those shared electrons are pulled depends on electronegativity, which is an atom’s ability to attract electrons in a bond. When atoms have similar electronegativities, they form nonpolar covalent bonds. When their electronegativities differ, the bond is polar because the electrons are shared unevenly. The number of covalent bonds an atom can make depends on its valence electrons. Oxygen has six valence...

ionic bonds

Ionic Compounds and Electrolytes

Ionic compounds form when atoms gain or lose electrons to reach a more stable electron configuration. The charged particles that result are called ions. Ionic bonds are electrostatic attractions between oppositely charged ions. The most reactive elements include those with one valence electron, such as potassium, and those that need one more valence electron, such as chlorine. Ions that lose electrons become positive cations. Ions that gain electrons become negative anions. Cations and anions...

hydrogen bonds

Hydrogen Bonds in Water

Hydrogen bonds in water are weak attractions between atoms that are already part of other chemical bonds. One atom is electronegative, such as oxygen, and carries a partial negative charge. The other is a hydrogen atom that is bonded to another electronegative atom and has a partial positive charge. These attractions form because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom like oxygen or nitrogen. The electrons in that bond are shared unequally.

van der waals interactions

Intermolecular Forces in Polar Solutions

Intermolecular forces are the attractions and repulsions that act between atoms and molecules. These electrostatic forces come from particles with permanent, partial, or temporary charges. For neutral atoms and molecules, the main types are ion-dipole, dipole-dipole, and dispersion forces, which are together called van der Waals forces. Polar molecules have a partial positive end and a partial negative end. That separation of charge creates a dipole. In water, oxygen is more electronegative...

elements and compounds

Elements, Compounds, and Bonding

Elements and compounds are the two main kinds of pure substances. A pure substance contains only one kind of matter. An element contains only one type of atom. A compound contains two or more types of atoms joined by a chemical bond. Elements can be atomic or molecular, depending on their basic units. They are unique forms of matter with specific chemical and physical properties. Ordinary chemical reactions cannot break an element into a smaller substance. There are 118 elements, but only 98...

molecular shapes

Electron Geometry and Lone Pairs

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chemical reactions

Atoms, Bonds, and Chemical Reactions

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

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

Water molecules stick to each other through cohesion. Water is neutral overall, but it is a polar molecule. The oxygen atom in one water molecule has a partial negative charge, and it can bind with a hydrogen atom that has a partial positive charge in another water molecule. This forms a hydrogen bond. Each water molecule can form up to four hydrogen bonds with other water molecules, and these bonds give water its cohesive nature. Cohesion helps water form droplets on a surface. Water does not...

adhesion

Water Climbing by Adhesion

Water can climb or stick to surfaces because of adhesion, which is the attraction between different kinds of molecules. In water, this is easy to see on polar surfaces such as glass or cellulose in plants. The positive hydrogen side of water is more attracted to the negative oxygen in silica than to nearby water molecules. This attraction helps explain capillary action. If a narrow glass tube is placed in a beaker of water, water molecules attach to the tube’s surface and the water level rises.

states of water

Water Phase Changes and Ice Density

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specific heat

How Specific Heat Affects Temperature

Specific heat capacity describes how much energy a substance needs to rise by 1 degree Celsius for each gram. It is often written with calories, grams, and degrees Celsius, but it can also be shown in joules, kilograms, and Kelvin. For water, 1 gram needs 1 calorie to increase by 1°C, which is also written as 1 cal/g-°C or 4186 J/kg/K. Water has a high specific heat capacity, so it takes in a large amount of heat before its temperature changes much. It also gives off a lot of heat when it...

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.

Electron Transfer in Redox | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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JoVE Core系列通过300多节动画视频课简明易懂地讲解生物学中的关键概念，以及150余段视频展示科学家在现代实验室开展实际研究实验，让生物学变得平易近人。

Minnesota Academic Standards in Science

Chemistry

3.1.1 9C.3.1.1.1

Alabama Course of Study Science

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.B.1.4.b

Florida Department of Education

High School

Life Science

SC.912.L.18

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Electron Transfer in Redox

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