Name: catalyst action in reaction rates
Uploaded: 2020-09-24T15:06:50.000Z
Duration: 2 min 50 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

Chemistry

Matter and its Interactions

PS.Chm.5.1

Catalysis

دراسة آليات وحركيات التفاعل،تساعد الباحثين في تحسين سرعة التفاعل. إن الزيادة في درجة الحرارة أو التركيز،ستزيد من معدل سرعة التفاعل،لكنها قد تؤدي كذلك إلى تحلل أو نواتج جانبية،إذا كانت الزيادة مفرطة. وعوضًا عن ذلك،هناك مواد كيميائية تزيد من معدل سرعة التفاعل،دون أن تتغير أو تُستهلك بشكل دائم،يمكن اضافتهاإلى خليط التفاعل.هذه المواد تُسمى محفزات،وتؤثر في ثابت معدل التفاعل بتغييرها طاقة التنشيط. تذكروا أنه كلما ارتفعت طاقة التنشيط،انخفض معدل سرعة التفاعل. وعليه،فالعديد من التفاعلات الكيميائية،كتحلل بيروكسيد الهيدروجين المائي،تتقدم ببطء.إضافة محفّز،يخفض طاقة التنشيط عن طريق تقديم آلية تفاعل بديلة دون أن تؤثر وضع الطاقة،في المواد المتفاعلة وفي النواتج. يوجد نوعان من المحفّزات متجانس وغير المتجانس. يتواجد المحفّز المتجانس في المرحلة ذاتها حيث تتواجد المواد المتفاعلة.على سبيل المثال،يُضاف بروميد الصوديوم إلى بيروكسيد الهيدروجين المائي،لزيادة سرعة تحلله إلى أكسجين في الحالة الغازية وماء. أولاًتتفاعل أيونات البروميد مع بيروكسيد الهيدروجين،داخل وسط حمضي لتشكل محلولًا برتقاليًا من البروم المائي والماء. وبعد ذلك،يتفاعل البروم المائي مع بيروكسيد الهيدروجين،وينتج عن ذلك أيونات بروميد،يدل على وجودها محلول عديم اللون.وكخاصية المحفزات،تعمل أيونات البروميد على زيادة سرعة التفاعل لكنها لا تُستهلك ولا تظهر في المعادلة الإجمالية المتوازنة. أما المحفّز غير المتجانس،فيتواجد بحالات مادية مختلفة،مقارنة بالمواد المتفاعلة. يمكن تقسيم المحفزات غير المتجانسة إلى أربع خطوات أساسية الادمصاص،الانتشار،التفاعل،والانتزاز على سبيل المثال،تفاعل الهدرجة الذي يحول غاز الإيثين غير المشبع إلى إيثان،تُزاد سرعته بواسطة نثر البالاديوم بدقة على الفحم النباتي.هنا يكون المحفز في حالة الصلابة،بينما المواد المتفاعلة في الحالة الغازية. أثناء عملية التحفيز غير المتجانسة هذه،تكون جزيئات الإيثين والهيدروجين طبقة رقيقة على سطح المحفّز. تتحطم الرابطة بين جزيئات الهيدروجين،فتسمح لذرات الهيدروجين بالانتشار على سطح المحفّز.عندما تواجه ذرات الهيدروجين المنتشرة جزيئات الإيثين على سطح المحفز،تتفاعل لتشكل الإيثان المشبع. وبعد ذلك،تُلفظ النواتج وتبتعد عن السطح المعدني،تاركة المحفز خلفها سليمًا.

التحفيز

يؤثر وجود عامل تحفيز في معدّل التفاعل الكيميائي. المحفّز هو مادة يمكنها زيادة معدّل التفاعل دون استهلاكها أثناء العملية. يمكن الحصول على فهم أساسي لدور العوامل المحفّزة’ أثناء التفاعلات الكيميائية من خلال مفهوم آليات التفاعل ومخطّطات الطاقة. <img alt="Image1" src="/files/ftp_upload/11383/11383_Image_1.png" style="text-align: center; height: 350px;" /> تمثل الصورة الموضحة الرسوم البيانية للتفاعل لعملية كيميائية ماصة للحرارة تتقدم في غياب (منحنى أحمر) ووجود (منحنى أزرق) العامل المحفّز. يمثل كلا المنحنيين نفس التفاعل الكلي – يبدأون وينتهون بنفس الطاقات. (في هذه الحالة، تحتوي المنتجات على طاقة أكثر من المواد المتفاعلة. وبالتالي، يكون التفاعل ماصاً للحرارة). ومع ذلك، فإن آليات تفاعلهم مختلفة. يستمر التفاعل غير المحفّز عبر آلية من خطوة واحدة (مع حالة انتقال واحدة ملحوظة). في المقابل، يتبع التفاعل المحفّز آلية من خطوتين (لوحظت حالتان انتقاليتان) مع طاقة تنشيط أقل بشكل ملحوظ. يوضح هذا الاختلاف في مسارات التفاعل دور المحفّز’ في توفير آلية تفاعل بديلة مع طاقة تنشيط أقل، وبالتالي تسريع التفاعلات. لا تحتاج آلية التفاعل المحفّز إلى تضمين عدد من الخطوات الأولية أكبر من الآلية غير المحفّزة. ومع ذلك، يجب أن يوفر مساراً بديلاً للتفاعل تكون خطوته لتحديد المعدل أسرع (مع طاقة أقل من Ea أو طاقة تنشيط). يمكن تصنيف التفاعل المحفّز على أنه متجانس أو غير متجانس، بناءً على الحالات الفيزيائية التي توجد بها المحفّزات والمتفاعلات أثناء العملية التحفيزية. التحفيز المتجانس في التحفيز المتجانس، يكون المحفّز موجوداً في نفس الطور مثل المواد المتفاعلة – صلبة أو سائلة أو غازية. أثناء العملية، يتفاعل المحفّز مع المادة المتفاعلة لتكوين مادة وسيطة، والتي تتحلل بعد ذلك أو تتفاعل مع مادة تفاعل أخرى في خطوة واحدة أو أكثر لتجديد المحفّز الأصلي وتشكيل المنتج النهائي. من الأمثلة على التحفيز المتجانس العملية الكيميائية التي تنطوي على تحلل الأوزون الذي يحدث في الغلاف الجوي العلوي للأرض’ الأوزون هو جزيء غير مستقر نسبياً يتحلّل لإنتاج الأكسجين ثنائي الذرة. يتوافق تفاعل التحلل مع الآلية التالية المكونة من خطوتين: <img alt="Eq1" src="/files/ftp_upload/11383/11383_Equation_1.png" style="text-align: center; height: 75px;" /> يمكن أن تحفّز العديد من المواد تحلل الأوزون. على سبيل المثال، يُعتقد أن تحلل الأوزون المحفّز بأكسيد النيتريك– يحدث عبر آلية الخطوات الثلاث التالية: <img alt="Eq2" src="/files/ftp_upload/11383/11383_Equation_2.png" style="text-align: center; height: 115px;" /> ومع ذلك، فإن التفاعل العام هو نفسه لكل من الآلية غير المحفّزة المكوّنة من خطوتين والآلية المحفّزة بـNO المكوّنة من ثلاث خطوات :<img alt="Eq3" src="/files/ftp_upload/11383/11383_Equation_3.png" style="text-align: center; height: 50px;" /> في التفاعل المحفّز، لاحظ أن أكسيد النيتروجين هو مادة متفاعلة في الخطوة الأولى للآلية ومنتج في الخطوة الأخيرة. هذه سمة مميزة أخرى للمحفّز: على الرغم من مشاركته في التفاعل الكيميائي، إلا أنه لا يتم استهلاكه بالتفاعل. بالإضافة إلى ذلك، في هذا التحفيز المتجانس، يوجد كلا من المادة المتفاعلة والمحفّز في الطور الغازي. التحفيز غير المتجانس في التحفيز غير المتجانس، يوجد المحفز في مرحلة مختلفة (عادة ما تكون صلبة) عن المواد المتفاعلة. تعمل هذه المحفّزات عموماً عن طريق توفير سطح نشط يمكن أن يحدث التفاعل عليه. تحدث تفاعلات الطور الغازي والسائل المحفّز بواسطة محفّزات غير متجانسة على سطح المحفّز وليس داخل الطور الغازي أو السائل. 
 عادةً ما يتضمن التحفيز غير المتجانس العمليات التالية: <ol><li> ادمصاص المادة (المواد) المتفاعلة على سطح المحفز </li><li> تنشيط المتفاعلات الممتزة </li><li> تفاعل المادة (المواد) المتفاعلة المدمصّة </li><li> انتزاز المنتج (المنتجات) من سطح المحفّز </li></ol><img alt="Image2" src="/files/ftp_upload/11383/11383_Image_2.png" style="text-align: center; height: 250px;" /> تمثل الصورة التوضيحية آلية التفاعل التي تتضمن التحفيز غير المتجانس للإيثين وغاز الهيدروجين على سطح نيكل صلب، لتكوين غاز الإيثان C2H4 + H2 ⟶ C2H6): (أ) يتم ادمصاص الهيدروجين على سطح النيكل. أثناء هذه العملية، تنكسر روابط هيدروجين-هيدروجين لتكوين روابط نيكل-هيدروجين. (ب) يتم ادمصاص الإيثين أيضاً على سطح النيكل عن طريق تكسير رابطة كربون-كربون وتشكيل روابط كربون–نيكل. (ج) تنتشر ذرات الهيدروجين عبر السطح وتشكل روابط كربون-هيدروجين جديدة عندما تصطدم لتكوين إيثان (C2H6). (د) يتم امتزاز جزيئات الإيثان من سطح النيكل. يستخدم التحفيز غير المتجانس لتصنيع منتجات كيميائية صناعية مثل الأمونيا وحمض النيتريك وحمض الكبريتيك والميثانول. تُستخدم المحفزات غير المتجانسة أيضاً في المحوّلات المحفّزة الموجودة في معظم السيارات التي تعمل بالبنزين. تم اقتباس هذا النص من <a href="https://openstax.org/books/chemistry-2e/pages/12-7-catalysis">Openstax, Chemistry 2e, Section 12.7: Catalysis</a>.

يؤثر وجود محفز على معدل التفاعل الكيميائي. المحفز هو مادة يمكنها زيادة معدل التفاعل دون استهلاكها ...

Education

JoVE Core

الكيمياء

واحد

Chemical Kinetics

الحركية الكيميائية

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

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 activation energy, or Ea. The lower rate-determining barrier is what makes the reaction faster.

Catalytic reactions are often grouped as homogeneous or heterogeneous. In homogeneous catalysis, the catalyst and reactants are in the same phase, which may be solid, liquid, or gas. The catalyst reacts with the reactant to form an intermediate, and that intermediate then breaks down or reacts again to form the product and regenerate the catalyst.

A good example of homogeneous catalysis is ozone decomposition in the upper atmosphere. Ozone breaks down to form diatomic oxygen, and nitric oxide can catalyze that process through a three-step mechanism. In this reaction, NO appears as a reactant in the first step and a product in the last step, which shows that it participates in the reaction but is not used up. Here, both the reactant and the catalyst are gases.

In heterogeneous catalysis, the catalyst is in a different phase from the reactants, usually a solid. These reactions happen on the catalyst surface. They typically include adsorption of reactants, activation on the surface, reaction of the adsorbed molecules, and desorption of the products.

The nickel-catalyzed reaction of ethene and hydrogen to form ethane shows this surface process. Hydrogen first adsorbs on nickel, and the H-H bond breaks to form nickel-hydrogen bonds. Ethene also adsorbs as its carbon-carbon pi bond breaks and nickel-carbon bonds form. Hydrogen atoms then move across the surface and make new carbon-hydrogen bonds, and the ethane product desorbs from the nickel surface.

Heterogeneous catalysts are important in industry. They help make ammonia, nitric acid, sulfuric acid, and methanol. They are also used in catalytic converters in most gasoline-powered cars.

Catalyst Action in Reaction Rates

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

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...

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

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 catalysts speed up reactions by lowering activation energy, with clear examples of homogeneous and heterogeneous catalysis for high school chemistry.

Catalyst Action in Reaction Rates | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

Pennsylvania State Academic Standards

Physical Science

Chemical Reactions

3.2.9-12.D

3.2.9-12.E

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Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.f

Arizona Science Standards

High School

HS.P1

HS.P1U1.3

Next Generation Science Standards

Matter and Its Interactions

HS-PS1-4

HS-PS1-5

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

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New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-5.

Georgia Standards of Excellence

SC4.

Catalysts in Chemical Reactions

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

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 ...

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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

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Catalyst Action in Reaction Rates

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