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

Reaction Mechanisms

Una reazione chimica è spesso rappresentata da un'equazione chimica bilanciata globale, che indica i reagenti e i prodotti. Tuttavia, la reazione effettiva è spesso più complessa, e si manifesta in più fasi. Per esempio, questa reazione dell'ossido nitrico con idrogeno, che forma azoto gassoso e acqua, avviene in tre distinte fasi successive.

Questi passaggi sono definiti nel meccanismo di reazione. Ogni fase del meccanismo di reazione è detta reazione elementare"e rappresenta l'interazione, come la rottura, o la formazione, del legame fra le specie che reagiscono. Molecole specifiche, come il biossido di diazoto e il protossido di azoto, si formano durante una fase elementare e si consumano durante un'altra.

Tali specie sono dette intermedi di reazione. Gli intermedi di reazione sono prodotti a bassa energia di una reazione elementare. Sono spesso di breve durata, il che spiega la loro assenza nella miscela di prodotti.

Gli intermedi di reazione non sono i medesimi dei complessi attivati. I complessi attivati sono stati di transizione ad alta energia, esistenti solo durante la trasformazione dei reagenti in prodotti. La combinazione dei passaggi elementari fornisce l'equazione per la complessiva reazione chimica.

Qui, gli intermedi di reazione vengono eliminati, e pertanto non compaiono nell'equazione chimica complessiva. Le diverse reazioni elementari possono progredire a velocità variabili. La fase elementare più lenta determina la velocità di reazione complessiva.

In questo caso, la reazione del biossido di diazoto con l'idrogeno gassoso è la fase limitante la velocità. Le reazioni elementari possono venire comunemente distinte in tre tipi, a seconda del numero di molecole che reagiscono, o della molecolarità. In una reazione unimolecolare, una singola molecola reagente si trasforma in uno o più prodotti.

In una reazione bimolecolare, reagiscono due molecole distinte. Una reazione termolecolare, benché alquanto rara, coinvolge tre molecole individuali, le quali reagiscono per produrre intermedi o prodotti. A differenza della legge di velocità per una reazione chimica complessiva, che è determinata sperimentalmente, le leggi di velocità per le reazioni elementari possono essere previste dai coefficienti stechiometrici dei loro reagenti.

In breve, la molecolarità di una reazione elementare corrisponde all'ordine di reazione globale del passaggio elementare. Pertanto, quelle unimolecolari sono spesso reazioni del primo ordine, le reazioni bimolecolari sono del secondo ordine, e le reazioni termolecolari sono del terzo ordine. La comprensione dei meccanismi di reazione e della cinetica aiuta i chimici a identificare ed ottimizzare le reazioni chimiche.

meccanismi di reazione

Le reazioni chimiche spesso avvengono in modo graduale, coinvolgendo due o più reazioni distinte che si svolgono in sequenza. Un'equazione bilanciata indica le specie reagenti e le specie prodotte, ma non rivela dettagli su come avviene la reazione a livello molecolare. Il meccanismo di reazione (o percorso di reazione) fornisce dettagli riguardanti il processo preciso e graduale attraverso il quale avviene una reazione.

Ad esempio, la decomposizione dell’ozono sembra seguire un meccanismo in due fasi:

<img alt="Eq1" src="/files/ftp_upload/11381/11381_Equation_1.png" style="text-align: center; height: 70px;" />

Ciascuno dei passaggi di un meccanismo di reazione è chiamato reazione elementare. Queste reazioni elementari si verificano in sequenza, come rappresentato nelle equazioni dei passaggi, e si sommano per produrre l'equazione chimica bilanciata che descrive la reazione complessiva:

<img alt="Eq2" src="/files/ftp_upload/11381/11381_Equation_2.png" style="text-align: center; height: 50px;" />

Si noti che l'atomo di ossigeno prodotto nella prima fase viene consumato durante la seconda e non appare come prodotto nella reazione complessiva. Tali specie che vengono prodotte in una fase e consumate in quella successiva sono chiamate intermedi di reazione.

Mentre l’equazione di reazione complessiva indica che due molecole di ozono reagiscono per dare tre molecole di ossigeno, il meccanismo di reazione effettivo non prevede la collisione diretta e la reazione di due molecole di ozono. Invece, un O_3 si decompone per produrre O_2 e un atomo di ossigeno, e una seconda molecola di O_3 reagisce successivamente con l'atomo di ossigeno per produrre due ulteriori molecole di O_2.

A differenza delle equazioni bilanciate che rappresentano una reazione complessiva, le equazioni per le reazioni elementari sono rappresentazioni esplicite del cambiamento chimico. Un'equazione di reazione elementare descrive il(i) reagente(i) effettivo(i) sottoposto(i) a rottura/formazione del legame e il(i) prodotto(i) formato(i). Pertanto, la legge sulla velocità di una reazione elementare può essere derivata direttamente dalla sua equazione chimica bilanciata. Tuttavia, questo non è il caso delle reazioni chimiche tipiche, per le quali le leggi di velocità possono essere determinate in modo affidabile solo tramite sperimentazione.

Reazioni elementari unimolecolari

La molecolarità di una reazione elementare è il numero di specie reagenti (atomi, molecole o ioni). Ad esempio, una reazione unimolecolare prevede la reazione di un singolo reagente per produrre una o più molecole di prodotto:

<img alt="Eq3" src="/files/ftp_upload/11381/11381_Equation_3.png" style="text-align: center; height: 50px;" />

La legge sulla velocità per una reazione unimolecolare è del primo ordine; tasso = k [A].

Una reazione unimolecolare può essere una delle numerose reazioni elementari in un meccanismo di reazione complesso. Ad esempio, la reazione (O_3 (g) → O_2 (g) + O) illustra una reazione elementare unimolecolare che si verifica come parte di un meccanismo di reazione in due fasi. Tuttavia, alcune reazioni unimolecolari possono essere l'unico passaggio di un meccanismo di reazione a passaggio singolo. (In altre parole, una reazione “complessiva” può anche essere una reazione elementare in alcuni casi.) Ad esempio, la decomposizione in fase gassosa del ciclobutano, C4H8, in etilene, C2H4, è rappresentata dall’equazione chimica:

<img alt="Eq3A" src="/files/ftp_upload/11381/11381_Equation_3A.png" style="text-align: center; height: 50px;" />

Questa equazione rappresenta la reazione complessiva, descrivendo un processo elementare unimolecolare. La legge cinetica prevista da questa equazione, assumendo che si tratti di una reazione elementare, risulta essere la stessa legge cinetica derivata sperimentalmente per la reazione complessiva, mostrando un comportamento del primo ordine:

<img alt="Eq4" src="/files/ftp_upload/11381/11381_Equation_4.png" style="text-align: center; height: 70px;" />

Questo accordo tra l’equazione cinetica osservata e prevista indica che il processo unimolecolare a fase singola proposto sia un meccanismo ragionevole per la reazione del butadiene.

Reazioni elementari bimolecolari

Una reazione bimolecolare coinvolge due specie reagenti. Per esempio:

<img alt="Eq5" src="/files/ftp_upload/11381/11381_Equation_5.png" style="text-align: center; height: 70px;" />

Nel primo tipo, dove le due molecole reagenti sono diverse, l’equazione cinetica è del primo ordine in A e del primo ordine in B (secondo ordine nel complesso)

<img alt="Eq6" src="/files/ftp_upload/11381/11381_Equation_6.png" style="text-align: center; height: 50px;" />

Nel secondo tipo, in cui due molecole identiche si scontrano e reagiscono, l’equazione cinetica è del secondo ordine in A:

<img alt="Eq7" src="/files/ftp_upload/11381/11381_Equation_7.png" style="text-align: center; height: 50px;" />

Alcune reazioni chimiche avvengono mediante meccanismi costituiti da una singola reazione elementare bimolecolare. Un esempio è la reazione del biossido di azoto con il monossido di carbonio:

<img alt="Eq8" src="/files/ftp_upload/11381/11381_Equation_8.png" style="text-align: center; height: 50px;" />

Le reazioni elementari bimolecolari possono anche essere coinvolte come fasi in un meccanismo di reazione a più fasi. La reazione dell'ossigeno atomico con l'ozono è la seconda fase di un meccanismo di decomposizione dell'ozono in due fasi:

<img alt="Eq9" src="/files/ftp_upload/11381/11381_Equation_9.png" style="text-align: center; height: 50px;" />

Reazioni elementari termolecolari

Una reazione termolecolare elementare comporta la collisione simultanea di tre atomi, molecole o ioni. Le reazioni elementari termolecolari sono rare perché la probabilità che tre particelle entrino in collisione simultaneamente è molto rara. Esistono, tuttavia, alcune reazioni elementari termolecolari consolidate. La reazione dell'ossido nitrico con l'ossigeno sembra coinvolgere passaggi termolecolari:

<img alt="Eq10" src="/files/ftp_upload/11381/11381_Equation_10.png" style="text-align: center; height: 70px;" />

Allo stesso modo, la reazione dell'ossido nitrico con il cloro sembra coinvolgere passaggi termolecolari:

<img alt="Eq11" src="/files/ftp_upload/11381/11381_Equation_11.png" style="text-align: center; height: 70px;" />

Spesso uno dei passaggi elementari in un meccanismo di reazione multifase è significativamente più lento degli altri. Poiché una reazione non può procedere più velocemente della fase più lenta, questa fase limiterà la velocità con cui avviene la reazione complessiva. La fase elementare più lenta è quindi chiamata fase di limitazione della velocità (o fase di determinazione della velocità) della reazione.

Questo testo è adattato da <a href="https://openstax.org/books/chemistry-2e/pages/12-6-reaction-mechanisms">Openstax, Chemistry 2e, 12.6: Reaction Mechanisms.</a>

Meccanismi di reazione

Le reazioni chimiche avvengono spesso in modo graduale, coinvolgendo due o più reazioni distinte che avvengono in sequenza. Un'equazione bilanciata indica ...

Education

Didattica

JoVE Core

Chimica

Chemical Kinetics

Cinetica Chimica

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

JoVE Core: Chimica illustra concetti chiave di chimica attraverso video animazioni concise e di immediata comprensione. Inoltre, i video della sezione "scienziati in azione" mostrano procedure metodologiche realizzate da ricercatori provenienti dai migliori laboratori internazionali.

Pennsylvania State Academic Standards

Physical Science

Chemical Reactions

3.2.9-12.D

3.2.9-12.E

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-4

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Interactions Of Matter

Chemical reactions

Virginia  Standards of Learning

HIgh School

CH.7

CH.7.e

Arizona Science Standards

HS.P1

HS.P1U1.3

Alabama Course of Study Science

Matter and Its Interactions: Energy

9-12.C.3.3.b

Next Generation Science Standards

Matter and Its Interactions

HS-PS1-2

HS-PS1-5

HS-PS1-7

Florida Department of Education

SC.912.P.12

SC.912.P.12.12

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS1-4

C-PS1-5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-5.

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 ...

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:


	...

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

Description

Transcript

Tags

More videos by Standards