Name: lewis structures, bonds, and formal charge
Uploaded: 2025-05-22T09:05:32.000Z
Duration: 2 min 19 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Chemistry

Matter and Its Interactions

CHEM1.PS1.12

Lewis Structures and Formal Charges

מבני לואיס הם ייצוגים פשוטים של קשרים כימיים בין אטומים. ניקח לדוגמה אתן, שבו שני אטומי פחמן בעלי ארבעה אלקטרונים ערכיים מוקפים כל אחד בארבעה אטומי מימן בעלי אלקטרון ערכיות אחד כל אחד. לפיכך, לאתן יש בסך הכל שנים עשר אלקטרונים ערכיים.
נדרשים עשרים וארבעה אלקטרונים כדי לספק את השמיניות לשני אטומי פחמן ואת הדואטים לארבעה אטומי מימן. לפיכך, שנים עשר אלקטרונים חייבים להיות משותפים בין האטומים. עם רק שנים עשר אלקטרונים זמינים, כולם חייבים להיות אלקטרונים קושרים כדי לאפשר לכל האטומים להגיע לתצורה אלקטרונית יציבה.
לפעמים, אטומים במבנים פוליאטומיים אינם מציגים את המספר הסטנדרטי של אלקטרונים ערכיים. במקרים כאלה, מטען פורמלי שאינו אפס, F, קשור לאטום החריג. המטען הצורני שווה למספר אלקטרונים ערכיים על האטום הנייטרלי פחות מספר הקשרים והאלקטרונים הבלתי משותפים על אותו אטום.
לדוגמה, ביון האמוניום, לכל אטום מימן יש אלקטרון ערכיות אחד בצורתו הניטרלית והוא קשור בקשר יחיד, המניב מטען פורמלי של אפס.
זה משאיר את אטום החנקן עם ארבעה אלקטרונים ערכיים במקום חמשת אלקטרונים הערכיות הרגילים שלו. מכיוון שחסר לו אלקטרון אחד, הוא נושא מטען פורמלי של אחד פלוס. לפיכך, המטען הכולל על יון האמוניום הוא אחד פלוס.
תצורות יציבות בדרך כלל ממזערות חיובים רשמיים. עבור יסודות גדולים יותר, ניתן להרחיב את השמינייה כך שתחלוק יותר משמונה אלקטרונים כדי להגיע לתצורה עם פחות מטענים צורניים.
לדוגמה, אטום הגופרית בתלת-תחמוצת הגופרית יכול ליצור קשרים יחידים וכפולים עם אטומי החמצן שמסביב. עם זאת, הסדר הקשר הכפול עדיף, שכן הוא מפחית את המטען הפורמלי הכולל על האטום.
חריגים אחרים לכלל השמינייה כוללים תרכובות נושאות בור, שמטרתן שישה אלקטרונים משותפים, ולא שמונה, מכיוון שהשגת שמינייה דורשת מטען פורמלי.

עובד מתוך <a href="https://openstax.org/books/chemistry-2e/pages/7-3-lewis-symbols-and-structures">Openstax, Chemistry 2e, Section 7.3: Lewis Symbols and Structures</a> and <a href="https://openstax.org/books/chemistry-2e/pages/7-4-formal-charges-and-resonance">Openstax, Chemistry 2e, Section 7.4: Formal Charges and Resonance</a>.

﻿מבני לואיס ומטענים פורמליים

<div style="direction:rtl"> ניתן להשתמש בסימנים של לואיס כדי לציין את היווצרותם של קשרים קוולנטיים, המוצגים במבני לואיס - רישומים המתארים את הקשר במולקולות וביונים רב-אטומיים. ניתן להשתמש בטבלה המחזורית כדי לחזות את מספר האלקטרונים הערכיים באטום ואת מספר הקשרים שייווצרו כדי להגיע לאוקטט. ליסודות מקבוצה 18, כגון ארגון והליום, יש קונפיגורציות אלקטרונים מלאות ולכן רק לעתים רחוקות משתתפים בקשרים כימיים. עם זאת, אטומים מקבוצה 17, כמו ברום או יוד, צריכים רק אלקטרון אחד כדי להגיע לאוקטט. לפיכך, אטומים השייכים לקבוצה 17 יכולים ליצור קשר קוולנטי יחיד. האטומים של קבוצה 16 צריכים שני אלקטרונים כדי להגיע לאוקטט; לפיכך, הם יכולים ליצור שני קשרים קוולנטיים. באופן דומה, פחמן, ששייך לקבוצה 14, זקוק לארבעה אלקטרונים נוספים כדי להגיע לאוקטט; לפיכך, פחמן יכול ליצור ארבעה קשרים קוולנטיים. חשבו על מבנה לואיס של מולקולת הכלור: <img alt="Figure1" src="/files/ftp_upload/11681/PTfigure_1.svg" style="text-align: center; height: 30px;"> מבנה לואיס מצביע על כך שלכל אטום Cl יש שלושה זוגות אלקטרונים שאינם משמשים בקשרים (הנקראים זוגות בודדים) וזוג אלקטרונים משותף (הכתוב בין האטומים). מקף (או קו) משמש לפעמים לציון זוג אלקטרונים משותף: Cl–Cl זוג אלקטרונים משותף אחד נקרא קשר יחיד. כל אטום Cl מקיים אינטראקציה עם שמונה אלקטרונים ערכיים: השישה בזוגות הבודדים והשניים בקשר היחיד. עם זאת, ייתכן שזוג אטומים יצטרך לחלוק יותר מזוג אלקטרונים אחד כדי להשיג את האוקטט הנדרש. קשר כפול נוצר כאשר שני זוגות אלקטרונים משותפים בין זוג אטומים, כמו בין אטומי הפחמן והחמצן ב-CH 2 O (פורמלדהיד). <img alt="Figure2" src="/files/ftp_upload/11681/PTfigure_2.svg" style="text-align: center; height: 60px;"> קשר משולש נוצר כאשר שלושה זוגות אלקטרונים משותפים לזוג אטומים, כמו בפחמן חד חמצני (CO). <img alt="Figure3" src="/files/ftp_upload/11681/PTfigure_3.svg" style="text-align: center; height: 20px;"> המטען הפורמלי של אטום במולקולה הוא המטען ההיפותטי שיהיה לאטום אם האלקטרונים בקשרים מחולקים באופן שווה בין האטומים. ניתן לחשב את המטען הפורמלי על ידי הפחתת הסכום של מספר האלקטרונים הלא-קושרים ומספר הקשרים על אטום (או מחצית ממספר האלקטרונים המחוברים) ממספר האלקטרונים הערכיים של האטום הנייטרלי: מטען פורמלי = # אלקטרוני מעטפת ערכיות (אטום חופשי) − # זוגות אלקטרונים בודדים − # קשרים ניתן לבדוק פעמיים את חישובי המטען הפורמלי על ידי קביעת סכום המטענים הפורמליים עבור המבנה כולו. סכום המטענים הפורמליים של כל האטומים במולקולה ניטרלית חייב להיות אפס; סכום המטענים הפורמליים ביון צריך להיות שווה למטען היון. זכור כי המטען הפורמלי המחושב עבור אטום אינו המטען בפועל של האטום במולקולה. המטען הפורמלי הוא רק הליך שימושי בחישוב דרגות חמצון; זה לא מצביע על נוכחות של מטענים בפועל. </div>

ניתן להשתמש בסמלי לואיס כדי לציין את היווצרותם של קשרים קוולנטים, המוצגים במבנים של לואיס – רישומים המתארים את הקשר ב...

Education

JoVE Core

Organic Chemistry

כימיה אורגנית

Unit 1

יחידה 1

Covalent Bonding and Structure

קשרים קוולנטיים ומבנה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

lewis structures, bonds, and formal charge

Lewis structures show how atoms share electrons in covalent bonds and in polyatomic ions. Lewis symbols help draw these structures, and the periodic table helps predict how many valence electrons an atom has and how many bonds it can form to reach an octet.

Group 18 elements, such as argon and helium, already have filled electron configurations. They rarely take part in chemical bonding. Atoms in group 17, such as bromine and iodine, need one more electron to reach an octet, so they can form one covalent bond. Atoms in group 16 need two electrons, so they can form two covalent bonds. Carbon is in group 14 and needs four more electrons, so it can form four covalent bonds.

The chlorine molecule is a simple example of a Lewis structure. Each Cl atom has three lone pairs, which are electron pairs not used in bonding, and one shared pair between the atoms. A dash or line can show this shared pair, so the bond can be written as Cl–Cl. A single shared pair is a single bond, and each chlorine atom reaches eight valence electrons when its lone pairs and bond are counted.

Some atoms must share more than one pair of electrons to complete an octet. A double bond forms when two pairs of electrons are shared, as in formaldehyde, CH2O, between carbon and oxygen. A triple bond forms when three electron pairs are shared, as in carbon monoxide, CO. These bond types help show how atoms connect in a molecule.

Formal charge is a bookkeeping tool for Lewis structures. It is the hypothetical charge an atom would have if bonding electrons were shared evenly. To calculate it, subtract the number of lone pair electrons and the number of bonds from the number of valence shell electrons in the free atom. The formal charges in a neutral molecule must add to zero, and the formal charges in an ion must add to the ion’s charge. Even so, formal charge is not the same as actual charge on an atom.

Lewis Structures, Bonds, and Formal Charge

what is organic chemistry?

Carbon Compounds in Everyday Life

Organic chemistry focuses on carbon compounds called organic compounds. These compounds may come from living things or be made by chemists. Carbon is the main element in them, and it bonds with other carbon atoms as well as hydrogen, oxygen, nitrogen, and sulfur. Carbon can form up to four strong bonds. That ability lets carbon atoms build chains and rings of many sizes, shapes, and levels of complexity. Not every carbon-containing substance is classified as organic. Carbonates, cyanides, and...

electronic structure of atoms

Atomic Orbitals and Quantum Numbers

Atomic orbitals and quantum numbers describe how electrons are arranged around the nucleus. An atom has a small, positively charged nucleus with electrons surrounding it. The nucleus contains protons and neutrons, and the quantum mechanical model gives a better picture of this structure than older models. Protons carry a +1 charge and have a mass of 1.0073 amu. Neutrons have no charge and have a mass of 1.0087 amu. Electrons carry a −1 charge and have a mass of 0.00055 amu. The number of...

electron configurations

How Electrons Fill Atomic Orbitals

Electron filling in atoms follows a set order based on orbital energy. The Aufbau principle says each new electron enters the lowest-energy subshell available. The Pauli exclusion principle says no two electrons can share the same set of four quantum numbers. Hund’s rule of maximum multiplicity says electrons stay unpaired in equal-energy orbitals when possible. The order of filling follows the relative energies of the subshells. A common sequence is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.

chemical bonds

Chemical Bonds: Types and Strength

Chemical bonds help atoms reach a full valence shell like the nearest noble gas. The main bond types are ionic, covalent, and metallic. Bond energy and bond length also help explain how strong a bond is. An ionic bond forms from electrostatic attraction between cations and anions. In many cases, one atom transfers electrons to another atom, and the ions form from that transfer. Ionic bonds have no defined direction because the attraction spreads evenly through three-dimensional space. A...

polar covalent bonds

Electronegativity in Polar Covalent Bonds

Polar covalent bonds form when atoms share electrons unevenly. This happens in covalent bonds between atoms that have similar, but not identical, tendencies to attract electrons. Nonmetal atoms often make these bonds with other nonmetals. Hydrogen gas, H2, is a simple example of a covalent bond between two hydrogen atoms. A covalent bond begins when two atoms move close enough for their valence orbitals to overlap. In hydrogen, the 1s orbitals overlap and the single electrons on each atom...

lewis structures and formal charges

Lewis structures show how atoms share electrons in covalent bonds and in polyatomic ions. Lewis symbols help draw these structures, and the periodic table helps predict how many valence electrons an atom has and how many bonds it can form to reach an octet. Group 18 elements, such as argon and helium, already have filled electron configurations. They rarely take part in chemical bonding. Atoms in group 17, such as bromine and iodine, need one more electron to reach an octet, so they can form...

vsepr theory

Molecular Shapes from Electron Pairs

Molecular shape can be predicted from the way electron pairs arrange around a central atom. Valence shell electron-pair repulsion theory, or VSEPR theory, uses a Lewis structure to count bonding pairs and lone electron pairs. The main idea is simple: electron pairs spread out as far as possible to reduce repulsion. In a molecule, the valence electrons around the central atom can be bonding pairs or lone pairs. Bonding pairs are found mainly between bonded atoms. Lone pairs stay on one atom and...

molecular geometry and dipole moments

Predicting Shape and Molecular Polarity

Molecular shape and molecular polarity can be predicted with VSEPR theory and dipole moments. Start by writing the Lewis structure of the molecule or polyatomic ion. Then count the electron groups around the central atom. Lone pairs and bonds both count as electron groups, and a single, double, or triple bond each counts as one region of electron density. Use that count to identify the electron-pair geometry. Next, use the number of lone pairs to determine the molecular structure. If more than...

resonance and hybrid structures

Resonance in Nitrite and Carbonate Ions

Resonance explains why some Lewis structures do not match the measured properties of a molecule or ion. When two or more Lewis structures have the same atom arrangement, the real electron distribution is an average of the structures shown. The nitrite anion, NO2−, is one example. It can be drawn in two ways, with the N–O and N=O bonds in different places. If nitrite had one single bond and one double bond, the two bond lengths should be different, because a double bond is shorter and stronger...

valence bond theory and hybridized orbitals

valence-bond-theory-and-hybridized-orbitals

Covalent Bond Overlap and Orbital Hybridization

Covalent bonds form when orbitals on two atoms overlap and their single electrons pair up. The bond is stronger when the overlap is greater. Maximum overlap happens when the orbitals meet along a direct line between the two nuclei. A sigma bond, or σ bond, is the kind of covalent bond found in a single bond in a Lewis structure. In a σ bond, electron density is concentrated along the internuclear axis. A pi bond, or π bond, forms when two p orbitals overlap side by side. In a π bond, the...

mo theory and covalent bonding

Bond Order and Molecular Orbitals

Molecular orbital theory explains how electrons are arranged in molecules. It treats electron regions in a molecule much like atomic orbitals in an atom. A molecular orbital is the region of space where a valence electron is most likely to be found. Molecular orbitals form through the linear combination of atomic orbitals, or LCAO. When atomic wave functions combine in phase, they create regions with high electron density. When they combine out of phase, they create nodes, or regions with no...

intermolecular forces and physical properties

intermolecular-forces-and-physical-properties

How Intermolecular Forces Affect Matter

Intermolecular forces are the attractions between molecules, and they help explain how matter behaves. These forces influence melting points, boiling points, and whether substances mix with one another. Water has a much higher boiling point than hexane, which shows that water has stronger intermolecular forces. Three main kinds of intermolecular interactions are covered here. They include ion-dipole forces, dipole-dipole interactions, and van der Waals forces, which include London dispersion...

solubility

Why Some Substances Dissolve in Water

Solution formation depends on how solutes and solvents interact. A solution is a homogeneous mixture made of a solvent, which is the larger part, and a solute, which is the smaller part. The physical state of a solution is usually the same as the solvent. Concentration is often described as dilute for a low amount of solute or concentrated for a high amount of solute. When a solute dissolves, its particles are surrounded by solvent species. This process is called solvation. If water is the...

introduction to functional groups

Functional Groups and Organic Molecules

Functional groups are groups of atoms with specific chemical properties that appear within organic molecules. They are sometimes shown as "R." These groups sit along the carbon backbone of macromolecules, which can form chains or rings of carbon atoms. Functional groups help functionalize a compound. That means they can give the molecule different physical and chemical properties. In organic chemistry, this change in group structure can strongly affect how a compound behaves. Common...

overview of advanced functional groups

Advanced Functional Groups in Organic Chemistry

Advanced functional groups are atom clusters in organic molecules that give those molecules specific chemical properties. They are sometimes shown as "R" in formulas. By changing the atoms attached to a carbon skeleton, a functional group can make a compound behave differently in physical and chemical reactions. This topic covers several major classes of organic compounds with advanced functional groups. Aromatic hydrocarbons include benzene. Phenol is another example and is also called...

key terms and concepts

Learn how Lewis structures show bonding, lone pairs, single, double, and triple bonds, and how to calculate formal charge in molecules and ions.

Lewis Structures, Bonds, and Formal Charge | JoVE K12

organic chemistry

JoVE Core Organic Chemistry explains basic concepts of stereochemistry, reactions, and mechanisms using concise and easy-to-understand animated video lessons. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide.

formula-mass-and-mole-concepts-of-compounds

Formula Mass and Mole Concepts of Compounds

Formula Mass of Covalent Compounds

Chemical formulas represent the elemental makeup of substances. For covalent compounds, the formula represents the ...

Expressing Solution Concentration

A solute is a component of a solution that is typically present at a much lower concentration than the solvent. Solute concentrations are often described ...

determining-the-mass-percent-composition-in-an-aqueous-solution

Determining the Mass Percent Composition in an Aqueous Solution

Source: Laboratory of Dr. Neal Abrams &#8212; SUNY College of Environmental Science and Forestry
Determining the composition of a solution is an important ...

Solutions and Concentrations

Source: Laboratory of Dr. Michael Evans &#8212; Georgia Institute of Technology
A solution is a homogeneous mixture containing some components in small ...

Reaction Stoichiometry

A balanced chemical equation provides a great deal of information in a very succinct format. Chemical formulas provide the identities of the reactants and ...

stoichiometry-product-yield-and-limiting-reactants

Stoichiometry, Product Yield, and Limiting Reactants

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas.
...

Understand and be prepared to use values specific to chemical processes: the mole, molar mass, molarity, and percent composition. EXPLANATION: During the early and mid-1800s, a tremendous amount of early research poured into building an understanding of the way that atoms combine. This work required analysis of the percent composition of different substances. Joseph Proust's work with tin oxides led him to publish his law of definite proportions noting that a given pure substance will have a constant ratio for the combination of elements making up the substance. Building on Proust's work, John Dalton published his law of multiple proportions and atomic theory noting that multiple patterns exist for the way that atoms combine, yet the combining atoms are invariable. Meanwhile Amedeo Avogadro hypothesizes that given equal pressures and temperatures, two equal volumes of gas will contain equal numbers of atoms. Acknowledging that the exact number of atoms was unknown in these gaseous volumes, the Latin word "mole" was used. "Mole" translates to "lump" recognizing the ambiguous quantity of gas. A number of attempts have been undertaken historically to quantify the mole. Robert Millikan's oil drop experiment revealed the change of a single electron, which could then be divided into Faraday's Constant for the charge of a mole of electrons. Dividing the charge of a mole of electrons by the charge of a single electron yields the number of electrons in a mole, $6.022\times10^{\wedge}23$. Students should be familiar with how to translate between the given quantities. Student's first use atomism/Dalton's atomic theory in third grade noting that matter is made up of particles too small to be seen. This the first time where students will undertake the process of counting these invisible particles. Electrolysis of water provides a tangible experience to demonstrate the constituent parts of water, though the definite proportions of water may not be easily seen due to the solubility of the gasses produced. The concept of relative mass can be explored by comparing small groups of like items. For example, relative masses of beans can be compared with pinto, white, and black beans. If bags are created with equal numbers of like beans, students can develop a concept of why the smallest bean will have a relative mass of 1, analogous to hydrogen.

CHEM1.PS1.1

Chemical Equations

Chemical equations represent the identities and relative quantities of substances involved in a chemical reaction. The substances undergoing reaction are ...

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 ...

Chemical Reactions

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or ...

Balancing Redox Equations

Electrochemistry is the science involved in the interconversion of electrical and chemical reactions. Such reactions are called reduction-oxidation, or ...

Demonstrate that atoms, and therefore mass, are conserved during a chemical reaction by balancing chemical reactions. EXPLANATION: Standard 7.PS1.4 explores the idea that chemical reactions are rearrangements of atoms, and students undertake the process of balancing chemical reactions with that standard in seventh grade. The introduction of molar masses in high school makes an explicit connection between the number of atoms, as previously investigated, and the actual masses of the atoms, permitting the collection of more concrete evidence for the conservation of mass in chemical reactions.

CHEM1.PS1.2

Reaction Yield

The theoretical yield of a reaction is the amount of product estimated to form based on the stoichiometry of the balanced chemical equation. The ...

A balanced chemical equation provides the information of chemical formulas of the reactants and products involved in the chemical change. A ...

Limiting Reactant

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. However, in ...

chemical-equilibria-systematic-approach-to-equilibrium-calculations

Chemical Equilibria: Systematic Approach to Equilibrium Calculations

In systems with multiple equilibria, the equilibrium calculations use a systematic approach involving a series of steps to make sure there are as many ...

Perform stoichiometric calculations involving the following relationships: mole- mole; mass-mass; mole-mass; mole- particle; and mass- particle. Show a qualitative understanding of the phenomenon of percent yield, limiting, and excess reagents in a chemical reaction through pictorial and conceptual examples. (states of matter liquid and solid; excluding volume of gasses). EXPLANATION: This standard builds on the idea that balancing chemical reactions provides evidence for conservation of mass and that the behavior of atoms follows predictable patterns. Students now have the opportunity to utilize this understanding as they perform and evaluate chemical reactions. (The concepts of limiting reagent and percent yield are presented; however, students are not expected to determine these values algebraically. Use of molar volume in stoichiometric processes is beyond the scope of this standard.)

CHEM1.PS1.3

Predicting Reaction Outcomes

Kinetics describes the rate and path by which a reaction occurs. In contrast, thermodynamics deals with state functions and describes the properties, ...

Introduction to Chemical Reactions

All chemical reactions begin with a reactant, the general term for one or more substances entering the reaction. Sodium and chloride ions, for example, ...

Chemical Reactions in Aqueous Solutions

Chemical substances interact in many different ways. Certain chemical reactions exhibit common patterns of reactivity. Due to the vast number of chemical ...

Precipitation Reactions

In a precipitation reaction, aqueous solutions of soluble salts react to give an insoluble ionic compound &#x2013; the precipitate. The reaction occurs ...

Oxidation-Reduction Reactions

Oxidation&ndash;Reduction Reactions

Earth&rsquo;s atmosphere contains about 20% molecular oxygen, O2, a chemically reactive gas that plays an essential ...

Oxidation Numbers

In redox reactions, the transfer of electrons occurs between reacting species. Electron transfer is described by a hypothetical number called the ...

Acids, Bases and Neutralization Reactions

An acid-base reaction is one in which a hydrogen ion, H+, is transferred from one chemical species to another. Such reactions are of central importance to ...

Synthesis and Decomposition Reactions

Synthesis and decomposition are two types of redox reactions. Synthesis means to make something, whereas decomposition means to break something. The ...

types-of-chemical-reactions-exchange-and-reversible

Types of Chemical Reactions: Exchange and Reversible

An exchange reaction is a chemical reaction in which both synthesis and decomposition occur, chemical bonds are both formed and broken, and chemical ...

Use the reactants in a chemical reaction to predict the products and identify reaction classes (synthesis, decomposition, combustion, single replacement, double replacement). EXPLANATION: Chemical reactions are rearrangements of atoms that follow predicable patterns. There are patterns both at the macroscopic level in the behavior of some of the reaction classes, as well as patterns in the rearrangements of the atoms underlying the reaction. Students should be able to predict the products of the reactions, which also requires the ability to recognize the general patterns for each type of reaction.

CHEM1.PS1.4

kinetic-molecular-theory-gas-laws-explain-properties-gas

Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

The test of the kinetic molecular theory (KMT) and its postulates is its ability to explain and describe the behavior of a gas. The various gas laws ...

basic-postulates-kinetic-molecular-theory-particle-size-energy

Basic Postulates of Kinetic Molecular Theory: Particle Size, Energy, and Collision

The ideal-gas equation, which is empirical, describes the behavior of gases by establishing relationships between their macroscopic properties. For ...

Ideal Gas Law

Derivation of the Ideal Gas Law
Gases are a fundamental state of matter. A gas is a collection of molecules that have a significant distance between their ...

gas-laws-boyle-s-gay-lussac-charles-avogadro-s-and-ideal-gas-law

Gas Laws: Boyle's, Gay-Lussac, Charles', Avogadro's, and Ideal Gas Law

Through experiments, scientists established the mathematical relationships between pairs of variables, such as pressure and temperature, pressure and ...

kinetic-molecular-theory-molecular-velocities-temperature-kinetic

Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy

The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a ...

Kinetic Theory of an Ideal Gas

A mole is defined as the amount of any substance that contains as many molecules as there are atoms in exactly 12 grams of carbon-12. An Italian scientist ...

applications-of-the-ideal-gas-law-molar-mass-density-and-volume

Applications of the Ideal Gas Law: Molar Mass, Density, and Volume

The volume occupied by one mole of a substance is its molar volume. The ideal gas law, PV = nRT, &nbsp;suggests that the volume of a given quantity of gas ...

Conduct investigations to explore and characterize the behavior of gasses (pressure, volume, and temperature), develop models to represent this behavior, and construct arguments to explain this behavior. Evaluate the relationship (qualitative and quantitatively) at STP between pressure and volume (Boyle's Law), temperature and volume (Charles' Law), temperature and pressure (Gay-Lussac Law) and moles and volume (Avogadro's Law), and evaluate and explain these relationships with respect to kinetic molecular theory. Be able to understand, establish, and predict the relationships between volume, temperature, and pressure using combined gas law both qualitatively and quantitatively. EXPLANATION: When exploring the behavior of gasses, it is important to consider experimental design. Experiments used to show the relationships between these sets of variables should include one independent and one dependent variable. Other variables should be held constant. Pressure should serve as the dependent variable because it cannot be manipulated directly. Avogadro's Law can be used to relate the amount of gas in two different containers in lieu of knowing actual number of gas particles in an individual container. Individual demonstrations can be performed to explore each of the different gas laws.

CHEM1.PS1.5

Ideal Gas Equation

The ideal gas equation is an equation of state that relates the state variables pressure, volume, temperature, and the number of moles of a hypothetical ...

Source: Laboratory of Dr. Andreas Z&#252;ttel - Swiss Federal Laboratories for Materials Science and Technology
The ideal gas law describes the behavior ...

real-gases-effects-intermolecular-forces-molecular-volume-deriving

Real Gases: Effects of Intermolecular Forces and Molecular Volume Deriving Van der Waals Equation

Thus far, the ideal gas law, PV = nRT, has been applied to a variety of different types of problems, ranging from reaction stoichiometry and empirical and ...

chemical-stoichiometry-gases-using-ideal-gas-law-to-determine

Chemical Stoichiometry and Gases: Using Ideal Gas Law to Determine Moles

Chemical stoichiometry describes the quantitative relationships between reactants and products in chemical reactions.

In addition to measuring quantities ...

pV-Diagrams

The pV diagram, which is a graph of pressure versus volume of the gas under study, is helpful in describing certain aspects of the substance. When the ...

Use the ideal gas law, PV = nRT, to algebraically evaluate the relationship among the number of moles, volume, pressure, and temperature for ideal gases. EXPLANATION: If students have collected data during investigations for CHEM1.PS1.5, these data can then be used to linearize. With pressure assigned as the dependent variable and plotted against (moles) (temperature)/volume, the slope of the graph will be the gas constant, yielding the ideal gas law. After developing the mathematical model, this model can be used to make predictions for other systems.

CHEM1.PS1.6

Separation of Mixtures via Precipitation

Source: Laboratory of Dr. Ana J. Garc&#237;a-S&#225;ez &#8212; University of T&#252;bingen
Most samples of interest are mixtures of many different ...

States of Matter and Phase Changes

The internal energy of a substance&#8212;the total kinetic energy of all its molecules and the potential energy of their associated forces&#8212;depends ...

Distillation: Vapor&ndash;Liquid Equilibria

Distillation is a separation technique that takes advantage of the boiling point properties of disparate elements in a mixture. To perform distillation, ...

Filtration

Filtration is the physical separation of solids from a fluid using a filtration medium.
The filtration medium is chosen depending on the purpose of ...

Centrifugation

Centrifugation is a method of separating suspended particles from a liquid by spinning in a centrifuge at a high number of revolutions per minute.
...

Sublimation

Sublimation is the direct phase transformation from the solid to the gaseous phase, bypassing the liquid state.
For example, solid carbon dioxide, or dry ...

recrystallization-solidsolution-equilibria

Recrystallization: Solid&ndash;Solution Equilibria

Recrystallization is a purification technique used to separate impurities from solid compounds. In this technique, no chemical reactions occur. Instead, ...

Precipitation and Co-precipitation

Precipitation and coprecipitation techniques can be applied to separate a mixture of ions.
When different ions form sparingly soluble salts with the same ...

Electrodeposition

During electrodeposition, ions are separated from a solution by deposition on an electrode in an electrolytic cell.
While reduction occurs at the cathode ...

extraction-partition-and-distribution-coefficients

Extraction: Partition and Distribution Coefficients

The distribution law or Nernst&#39;s distribution law is the law that governs the distribution of a solute between two immiscible solvents. This law, also ...

Extraction: Effects of pH

Consider a weak base,&#160; B, with a partition coefficient, K, between the organic and aqueous phases.&#160;&#160;
While organic bases are usually more ...

Extraction: Advanced Methods

Metal ions can be separated by complexation with organic ligands to form uncharged chelates.
The chelating agent must contain hydrophobic groups and ...

Chromatography: Introduction

Chromatography is a technique used to separate compounds based on differences of partitioning between two phases, the stationary phase and the mobile ...

Dialysis

Dialysis separates desired analyte ions or molecules from unwanted molecules, or &#39;interferents&#39;, by allowing the sample solution to diffuse ...

Analyze solutions to identify solutes and solvents, quantitatively analyze concentrations (molarity, percent composition, and ppm), and perform separation methods such as evaporation, distillation, and/or chromatography and show conceptual understanding of distillation. Construct argument to justify the use of certain separation methods under different conditions. EXPLANATION: In seventh grade, students developed an understanding that chemical and physical properties of a sample of matter could be used to identify a substance. Building on this understanding, students now explore the use of these physical and chemical properties to separate mixtures. Analysis of the substances is performed to aid in further discussion and facilitate further quantitative analysis.

CHEM1.PS1.7

Acids and bases play several important roles in biology. The pH of a biological system can significantly impact the function of biological molecules, ...

Identify acids and bases as a special class of compounds with a specific set of properties. EXPLANATION: The concept of pH is first introduced in seventh grade as a chemical property of matter. Students should be introduced to multiple explanations of acid and base behavior to permit classification of common substances (e.g. baking soda, ammonia, carbon dioxide) as acids or bases. To further develop discussions of solubility, qualitative discussions of the differences between strong and weak acids are appropriate. (Calculations of pH or ion concentrations are beyond the scope of this standard. Discussions of pOH are beyond the scope of this standard. Conjugate pairs are beyond the scope of this standard.)

CHEM1.PS1.8

Lewis Structures, Bonds, and Formal Charge

Description

Transcript

More videos by Standards