Name: elementary steps in reaction mechanisms
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 3 min 6 s
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K12 Standards

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

North Carolina K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.5.1

Reaction Mechanisms

يُعبّر عن التفاعل الكيميائي،غالبًا،بمعادلة كيميائية متوازنة تُبيّن المواد المتفاعلة والنواتج. غير أن التفاعل الحقيقي،غالبًا ما يكون أكثر تعقيدًا ويمرّبخطوات عديدة. على سبيل المثال،هذا التفاعل بين أكسيد النيتروجين وبين الهيدروجين لتكوين غاز النيتروجين والماء يمرّبثلاث خطوات واضحة ومتعاقبة.هذه الخطوات تُسمى آلية التفاعل. كل خطوة في آلية التفاعل،تُسمى تفاعلًا أوليًا وتمثل التفاعل،مثل تحطيم الروابط أو تشكيلها،فيما بين الأصناف المتفاعلة. جزيئات معينة،كثاني أكسيد ثنائي النيتروجين وأكسيد النيتروز،تتشكل أثناء إحدى الخطوات الأولية وتُستهلك أثناء خطوة أولية أخرى.مثل هذه الأصناف تُسمى مركبات التفاعل الوسطية. المركبات الوسطية نواتج ذات طاقة متدنية تنتج عن تفاعل أولي. وغالبًا ما تكون حياتها قصيرة مما يفسر غيابها في الخليط الناتج.مركبات التفاعل الوسطية تختلف عن المعقدات المنَشّطة. المعقدات المنشّطة حالات انتقال ذات طاقة عالية،تتواجد فقط أثناء تحوّل المواد المتفاعلة إلى نواتج. دمج الخطوات الأولية يعطينا المعادلة للتفاعل الكيميائي الكلي.هنا جرى حذف المركبات الوسطية وبالتالي لا تظهر في المعادلة الكيميائية النهائية. قد تسير التفاعلات الأولية بسرعات متفاوتة. الخطوة الأولية الأبطأ هي التي تحدد معدل التفاعل الكلي.هنا تفاعل ثاني أكسيد ثنائي النيتروجين،مع غاز الهيدروجين،هو الخطوة التي تحد من معدل التفاعل. يمكن تصنيف التفاعلات الأولية عمومًا في ثلاثة أصناف،بناءًعلى عدد الجزيئات المتفاعلة المُسمى جزيئية. في تفاعل أحادي الجزيء،يتحول جزيء مادة متفاعلة واحد إلى ناتج أو أكثر.وفي تفاعل ثنائي الجزيء،يتفاعل جزيئان منفصلان. وفي التفاعلات ثلاثية الجزيء،وهي نادرة جدًا،تتفاعل ثلاثة جزيئات منفصلة لتعطي مركبات متوسطة أو نواتج. خلافًا لقانون معدل التفاعل الكيميائي الكلي،الذي يُحدد تجريبيًا،يمكن التنبؤ بقوانين معدلات التفاعلات الأولية،من خلال مُعاملات القياس المتكافئ للمواد المتفاعلة.باختصار،جزيئية تفاعل أولي ما تطابق الترتيب الكلي لخطوات التفاعلات الأولية. وعليه فإن التفاعلات أحادية الجزيء غالبًا ما تكون الأولى في الترتيب،وتأتي التفاعلات ثنائية الجزيء في الترتيب الثاني،وثلاثية الجزيء في الترتيب الثالث. فهم آليات التفاعلات وبياناتها الحركية يساعد الكيميائيين في تحديد و تحسين التفاعلات الكيميائية.

آليات التفاعل

غالباً ما تحدث التفاعلات الكيميائية بطريقة متدرجة، تتضمن تفاعلين مميزين أو أكثر تحدث في تسلسل. تشير المعادلة المتوازنة إلى الأنواع المتفاعلة وأنواع المنتجات، ولكنها لا تكشف عن أي تفاصيل حول كيفية حدوث التفاعل على المستوى الجزيئي. توفر آلية التفاعل (أو مسار التفاعل) تفاصيل تتعلق بالعملية الدقيقة خطوة بخطوة التي يحدث بها التفاعل. على سبيل المثال، يبدو أن تحلل الأوزون يتبع آلية ذات خطوتين: <img alt="Eq1" src="/files/ftp_upload/11381/11381_Equation_1.png" style="text-align: center; height: 70px;" /> تسمى كل خطوة من خطوات آلية التفاعل تفاعل أولي. تحدث هذه التفاعلات الأولية بالتسلسل، كما هو موضح في معادلات الخطوة، وهي تُجمع لتنتج المعادلة الكيميائية المتوازنة التي تصف التفاعل الكلي: <img alt="Eq2" src="/files/ftp_upload/11381/11381_Equation_2.png" style="text-align: center; height: 50px;" /> لاحظ أن ذرة الأكسجين الناتجة في الخطوة الأولى يتم استهلاكها خلال الثانية ولا تظهر كمنتج في التفاعل الكلي. تسمى هذه الأنواع التي يتم إنتاجها في خطوة واحدة واستهلاكها في خطوة لاحقة بمواد وسيطة. بينما تشير معادلة التفاعل الكلية إلى أن جزيئي أوزون يتفاعلان لإعطاء ثلاثة جزيئات أكسجين، فإن آلية التفاعل الفعلية لا تتضمن التصادم المباشر ورد فعل جزيئي أوزون. بدلاً من ذلك، يتحلل واحد من O3 لينتج O2 وذرة من الأكسجين، وتتفاعل جزيئة ثانية من O3 لاحقًا مع ذرة الأكسجين لينتج عن ذلك جزيئتين إضافيتين من O2 . على عكس المعادلات المتوازنة التي تمثل تفاعلاً كلياً، فإن معادلات التفاعلات الأولية هي تمثيلات صريحة للتغير الكيميائي. تصور معادلة التفاعل الأولية المتفاعل (المتفاعلات) الفعلية التي تخضع لكسر/صنع الرابطة، والمنتج (المنتجات) المتكونة. وبالتالي، يمكن اشتقاق قانون معدل التفاعل الأولي مباشرة من معادلته الكيميائية المتوازنة. ومع ذلك، ليس هذا هو الحال بالنسبة للتفاعلات الكيميائية النموذجية، حيث يمكن تحديد قوانين المعدل بشكل موثوق فقط من خلال التجارب. التفاعلات الأولية أحادية الجزيء إن جزيئية التفاعل الأولي هي عدد الأنواع المتفاعلة (الذرات أو الجزيئات أو الأيونات). على سبيل المثال، يتضمن التفاعل أحادي الجزيء تفاعل مفاعل واحد لإنتاج جزيء واحد أو أكثر من المنتج: <img alt="Eq3" src="/files/ftp_upload/11381/11381_Equation_3.png" style="text-align: center; height: 50px;" /> قانون معدل التفاعل أحادي الجزيء هو معدّل من الدرجة الأولى؛ المعدّل = k [A]. قد يكون التفاعل أحادي الجزيء واحداً من عدة تفاعلات أولية في آلية تفاعل معقدة. على سبيل المثال، التفاعل (O3 (g) → O2 (g) + O) يوضح تفاعلاً أولياً أحادي الجزيء يحدث كجزء من آلية تفاعل من خطوتين. ومع ذلك، قد تكون بعض التفاعلات أحادية الجزيء هي الخطوة الوحيدة لآلية التفاعل أحادية الخطوة. (بعبارة أخرى، قد يكون تفاعل “إجمالي” تفاعلاً أولياً أيضاً في بعض الحالات.) على سبيل المثال، تحلل الطور الغازي لـسيكلوبوتان C4H8، إلى الإيثيلين، C2H4، تمثلها المعادلة الكيميائية: <img alt="Eq3A" src="/files/ftp_upload/11381/11381_Equation_3A.png" style="text-align: center; height: 50px;" /> تمثل هذه المعادلة التفاعل الكلي، وتصف عملية أولية أحادية الجزيء. يتضح أن قانون المعدل المتوقع من هذه المعادلة، بافتراض أنه تفاعل أولي، هو نفسه قانون المعدل المشتق تجريبياً للتفاعل الكلي، والذي يوضح سلوك الدرجة الأولى للتفاعل: <img alt="Eq4" src="/files/ftp_upload/11381/11381_Equation_4.png" style="text-align: center; height: 70px;" /> يشير هذا الاتفاق بين قوانين المعدل المُلاحظ والمتوقع إلى أن العملية المقترحة أحادية الجزيء أحادية الخطوة هي آلية معقولة لتفاعل البوتاديئين. التفاعلات الأولية ثنائية الجزيئية يتضمن التفاعل ثنائي الجزيء نوعين متفاعَلين. على سبيل المثال: <img alt="Eq5" src="/files/ftp_upload/11381/11381_Equation_5.png" style="text-align: center; height: 70px;" /> في النوع الأول، حيث يختلف جزيء المتفاعلان، يكون قانون المعدل من الدرجة الأولى في A ومن الدرجة الأولى في B (الترتيب الثاني بشكل عام) 
 <img alt="Eq6" src="/files/ftp_upload/11381/11381_Equation_6.png" style="text-align: center; height: 50px;" /> في النوع الثاني، حيث يصطدم جزيءان متطابقان ويتفاعلان ، يكون قانون المعدل هو الترتيب الثاني في A:<img alt="Eq7" src="/files/ftp_upload/11381/11381_Equation_7.png" style="text-align: center; height: 50px;" /> تحدث بعض التفاعلات الكيميائية بواسطة آليات تتكون من تفاعل أولي ثنائي الجزيء واحد. أحد الأمثلة على ذلك هو تفاعل ثاني أكسيد النيتروجين مع أول أكسيد الكربون: <img alt="Eq8" src="/files/ftp_upload/11381/11381_Equation_8.png" style="text-align: center; height: 50px;" /> يمكن أيضاً تضمين التفاعلات الأولية ثنائية الجزيء كخطوات في آلية تفاعل متعددة الخطوات. تفاعل الأكسجين الذرّي مع الأوزون هو الخطوة الثانية لعملية تحلّل الأوزون والمكونة من خطوتين: <img alt="Eq9" src="/files/ftp_upload/11381/11381_Equation_9.png" style="text-align: center; height: 50px;" />التفاعلات الأولية الجزيئية يتضمن التفاعل الأولي الجزيئي التصادم المتزامن لثلاث ذرات أو جزيئات أو أيونات. التفاعلات الأولية الجزيئية غير شائعة لأن احتمال اصطدام ثلاث جسيمات في وقت واحد نادر جداً. ومع ذلك، هناك عدد قليل من التفاعلات الأولية الجزيئية النهائية. يبدو أن تفاعل أكسيد النيتريك مع الأكسجين يتضمن خطوات جزيئية نهائية: <img alt="Eq10" src="/files/ftp_upload/11381/11381_Equation_10.png" style="text-align: center; height: 70px;" /> وبالمثل، يبدو أن تفاعل أكسيد النيتريك مع الكلور يتضمن خطوات جزيئية نهائية: <img alt="Eq11" src="/files/ftp_upload/11381/11381_Equation_11.png" style="text-align: center; height: 70px;" /> غالباً ما تكون إحدى الخطوات الأولية في آلية التفاعل متعدد الخطوات أبطأ بكثير من الخطوات الأخرى. نظراً لأن التفاعل لا يمكن أن يستمر بشكل أسرع من أبطأ خطواته، فإن هذه الخطوة ستحد من معدل حدوث التفاعل الكلي. ولذلك فإن أبطأ خطوة أولية تسمى خطوة تحديد المعدل (أو خطوة تحديد المعدل) للتفاعل. هذا النص مقتبس من <a href="https://openstax.org/books/chemistry-2e/pages/12-6-reaction-mechanisms">Openstax, Chemistry 2e, 12.6: Reaction Mechanisms.</a>

غالبا ما تحدث التفاعلات الكيميائية بطريقة تدريجية ، تتضمن تفاعلين أو أكثر متميزين يحدثان في تسلسل. تشير المعادلة المتوازنة إلى ...

Education

JoVE Core

الكيمياء

واحد

Chemical Kinetics

الحركية الكيميائية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

elementary steps in reaction mechanisms

Chemical reactions can happen in steps, and a balanced equation does not show the full path at the molecular level. A reaction mechanism, also called a reaction path, gives the step-by-step process that explains how reactants become products. The decomposition of ozone is one example of a reaction that can be described by a sequence of steps.

Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and when they are added together, they give the balanced equation for the overall reaction. In the ozone example, an oxygen atom is made in the first step and used up in the second step, so it does not appear in the final equation. A species made in one step and used up in a later step is called a reaction intermediate.

The overall equation may show two ozone molecules forming three oxygen molecules, but the mechanism shows that the two ozone molecules do not react directly with each other. Instead, one O3 molecule breaks down to form O2 and an oxygen atom. Then a second O3 molecule reacts with that oxygen atom to make two more O2 molecules. This is why elementary reaction equations give a more direct picture of bond breaking and bond making than the overall equation does.

For an elementary reaction, the rate law can often be written directly from the balanced equation for that step. For most chemical reactions, the rate law must be found by experiment. That is why elementary reactions are useful when chemists build a mechanism that matches the observed behavior of a reaction.

Elementary reactions are described by molecularity, which is the number of reactant species in the step. A unimolecular reaction has one reactant species and forms one or more products. Its rate law is first order, written as rate = k[A]. A unimolecular step may be part of a larger mechanism, such as O3(g) → O2(g) + O in ozone decomposition. Some unimolecular reactions are also the whole reaction, not just one step. The gas-phase decomposition of cyclobutane, C4H8, to ethylene, C2H4, is one example, and its first-order experimental rate law agrees with the rate law predicted for an elementary single-step process.

A bimolecular reaction involves two reactant species. If the two reactants are different, the rate law is first order in A and first order in B, for a second-order overall rate. If the two reacting molecules are the same, the rate law is second order in A. Some reactions occur by a single bimolecular elementary reaction, such as the reaction of nitrogen dioxide with carbon monoxide. Bimolecular steps can also appear in multistep mechanisms, including the reaction of atomic oxygen with ozone in ozone decomposition.

A termolecular reaction involves the simultaneous collision of three atoms, molecules, or ions. These reactions are uncommon because three particles colliding at the same time is very unlikely. Still, a few termolecular elementary reactions are known. The reaction of nitric oxide with oxygen and the reaction of nitric oxide with chlorine both appear to involve termolecular steps.

In many multistep mechanisms, one elementary step is much slower than the others. A reaction cannot proceed faster than its slowest step, so that step controls the overall rate. This slowest step is called the rate-limiting step, or rate-determining step.

Elementary Steps in Reaction Mechanisms

reaction rate

Measuring Reaction Rates

Measuring reaction rates shows how fast reactants are used up or products are formed over time. The rate of reaction is the change in the amount of a reactant or product per unit time. Because of that, scientists measure how a property changes as the reaction proceeds and connect that change to reactant or product amounts. For reactions that make or use a gas, the rate can be followed by changes in volume or pressure. A rate expression is the mathematical way to write how concentration changes...

measuring reaction rates

Tracking Reaction Kinetics with Light and Pressure

Reaction kinetics can be tracked with polarimetry, spectrometry, and pressure measurements. These methods let scientists follow a reaction without disturbing the sample. They also help determine how reactant or product concentrations change over time. Polarimetry is used for optically active substances. These substances rotate the plane of polarized light, which is called optical rotation. The effect comes from molecular structure. Normal monochromatic light is unpolarized, but after it passes...

concentration and rate law

Reaction Order from Concentration

Reaction order from concentration shows how reactant amounts affect reaction rate. Rate laws, also called differential rate laws or rate equations, are mathematical expressions that connect reaction rate with the concentrations of reactants. For a generic reaction a A + b B → products, the rate law can be written using the reactant concentrations [A] and [B] and a rate constant k. In a rate law, k is the rate constant for one specific reaction at one specific temperature. The exponents m and n...

determining order of reaction

Finding Rate Law from Initial Rates

Rate laws connect the speed of a chemical reaction to the concentration of its reactants. The rate constant, k, and the reaction orders are not taken from the chemical equation. They are found experimentally by watching how the rate changes when the reactant concentrations change. One common way to do this is the method of initial rates. In this method, several trials are run with different starting concentrations. The measured rates are then compared to determine the reaction orders and,...

the integrated rate law: the dependence of concentration on time

the-integrated-rate-law-the-dependence-of-concentration-on-time

Reading Reaction Progress with Integrated Laws

Integrated rate laws connect reaction concentration to time. They help show how much reactant or product is present after a certain period. They can also help estimate how long a reaction must run to reach a given extent. A common use is finding how long radioactive material must be stored before its radioactivity drops to a safe level. These equations come from the differential rate law after it is integrated with respect to time. For a first-order reaction, where rate = k[A], the integrated...

half-life of a reaction

Reaction Half-Life in Kinetics

Reaction half-life is the time needed for half of a reactant to be consumed. After each half-life, half of the remaining reactant is used up. A hydrogen peroxide decomposition example shows this pattern clearly. The concentration drops from 1.000 M to 0.500 M in the first 6.00 hours, then to 0.250 M in the next 6.00 hours, and then to 0.125 M in the third period. Each later 6.00-hour interval removes half of what is left. For first-order reactions, the half-life does not depend on the reactant...

temperature dependence on reaction rate

Collision Theory and Reaction Speed

Collision theory explains why reaction speed depends on how particles collide. Atoms, molecules, or ions must come close together before they can react. The theory says the reaction rate depends on the collision rate, the orientation of the colliding species, and whether the collision has enough energy for bonds to change. A gas-phase reaction between carbon monoxide and oxygen shows why orientation matters. The molecules can collide in more than one way. If the oxygen side of carbon monoxide...

arrhenius plots

Determining Activation Energy from Temperature

The Arrhenius equation links activation energy and the rate constant, k, for chemical reactions. It is written as k = Ae−Ea/RT. In this equation, R is the ideal gas constant with a value of 8.314 J/mol·K, T is the temperature on the kelvin scale, Ea is the activation energy in J/mole, e is the constant 2.7183, and A is the frequency factor. The frequency factor depends on collision frequency and the orientation of reacting molecules. Experimental kinetic data can be used to find the activation...

reaction mechanisms

Chemical reactions can happen in steps, and a balanced equation does not show the full path at the molecular level. A reaction mechanism, also called a reaction path, gives the step-by-step process that explains how reactants become products. The decomposition of ozone is one example of a reaction that can be described by a sequence of steps. Each step in a mechanism is an elementary reaction. These elementary reactions happen in order, and when they are added together, they give the balanced...

rate-determining steps

Reaction Bottlenecks in Chemical Kinetics

Reaction bottlenecks help explain rate-determining steps in multistep reaction mechanisms. In a mechanism with several elementary steps, one step is often much slower than the others. That slowest step is called the rate-limiting step, or rate-determining step. A reaction cannot move faster than its slowest step, so this step controls the overall reaction rate. The idea is like traffic on a four-lane freeway with one lane closed. Cars can only move as fast as the bottleneck allows. In the same...

catalysis

Catalyst Action in Reaction Rates

Catalysts change the rate of a chemical reaction by giving it a faster path. A catalyst increases reaction rate without being consumed during the process. Its effect is often explained with reaction mechanisms and energy diagrams. For an endothermic reaction, the reactants and products start and end at the same energies in both cases. The uncatalyzed path is a one-step mechanism with one transition state. The catalyzed path follows a different mechanism with two transition states and a lower...

enzymes

Enzyme Action and Inhibition

Enzymes are biological catalysts that speed up many reactions in living organisms. They help control cellular metabolism by lowering the activation energy needed for biochemical reactions. When activation energy drops, reaction rates can increase. Enzyme problems can also lead to serious disease. A genetic abnormality that causes G6PD, or glucose-6-phosphate dehydrogenase, deficiency can disrupt the pathway that supplies NADPH to cells. In red blood cells, this can reduce glutathione and...

key terms and concepts

Explore how chemical reactions happen in steps, including elementary reactions, reaction intermediates, molecularity, rate laws, and the rate-limiting step.

Elementary Steps in Reaction Mechanisms | JoVE K12

chemistry

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Pennsylvania State Academic Standards

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Chemical Reactions

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Matter And Its Interactions

HS-PS1-4

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HS.P1

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Matter and Its Interactions: Energy

9-12.C.3.3.b

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New York State Science Learning Standards

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HS-PS1-5.

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Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Resonance

The Lewis structure of a nitrite anion (NO2&minus;) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O ...

Formal Charges

In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to ...

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

Analyze the structure of atoms and isotopes.

Elementary Steps in Reaction Mechanisms

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