Name: ester formation and everyday fragrances
Uploaded: 2020-03-26T07:22:29.000Z
Duration: 3 min 48 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Physical Science

SC.912.P.8

SC.912.P.8.13

Esterification

אסטרים הם קבוצה של מולקולות אורגניות שיכולות להיות בעלות ארומה פירותית או פרחונית. המבנה של אסטר הוא קרבוניל עם קבוצת אלקיל או אריל בצד אחד וחמצן הקשור לקבוצת אלקיל או אריל אחרת בצד השני.
בהתאם לקבוצות אלקיל או אריל, האסתר יכול לקבל מאפיינים רבים ושונים. לדוגמה, התגובה של גליצרול ושלוש חומצות שומן, שהן חומצות קרבוקסיליות עם שרשראות אלקיל ארוכות, גורמת לטריגליצרידים, שיש להם שלוש קבוצות אסטר. שרשראות אלקיל ארוכות מחומצות השומן מעניקות לטריגליצרידים משקל מולקולרי גבוה מאוד. לעומת זאת, אסטרים פשוטים הם בעלי משקל מולקולרי נמוך וקבוצות פונקציונליות קטנות.
הריחות והטעמים של פירות ופרחים מיוחסים לאסתרים פשוטים. אפילו שינויים קטנים במבנה של אסטר פשוט משפיעים מאוד על ניחוחו. לדוגמה, שינוי קבוצת הידרוקסיל לאמין משנה את ריחו של אסטר זה מווינטרגרין לענבים. באופן דומה, פרופיל אצטט מריח כמו אגסים, בעוד שבוטיל אצטט, שיש לו רק עוד פחמן אחד בשרשרת, מריח כמו תפוחים.
אחת הדרכים הנפוצות להכין אסטר היא אסטריפיקציה של פישר, שבה חומצה קרבוקסילית ואלכוהול מגיבים בנוכחות זרז חומצה ליצירת האסתר והמים. קבוצת R וקבוצת הקרבוניל מגיעות מהחומצה הקרבוקסילית, וקבוצת האלקוקסי או הארילוקסי עם ה-R מגיעה מהאלכוהול. תגובת אסטריפיקציה זו הפיכה. עם תערובת של 1 עד 1 של חומצה קרבוקסילית ואלכוהול, הוא נוטה להגיע לשיווי משקל עם תשואה של כ -70% של האסתר במקרה הטוב.
עם זאת, העיקרון של לה שטלייה מאפשר לנו להגדיל את התשואה של האסתר מעבר לכך. העיקרון של לה שטלייה קובע שכל מערכת בשיווי משקל כימי הנתונה לשינוי בריכוז, בלחץ, בטמפרטורה או בנפח תתאים את עצמה לשיווי משקל חדש המנטרל את השינוי.
לכן, אם נגדיל את ריכוזו של אחד המגיבים בתגובה הפיכה, שיווי המשקל ינוע לכיוון שמקטין את ריכוזו. התוצאה היא תשואה גבוהה יותר של מוצר האסתר בשיווי משקל. לכן, אנו יכולים לשפר את התשואה של אסטריפיקציה באמצעות יחס מולארי 3: 1 או 1: 3 של חומצה קרבוקסילית לאלכוהול.
בניסוי זה, אסטריפיקציה של פישר תבוצע באמצעות אלכוהול עודף וחומצה גופרתית כזרז. בתגובה זו, תגובת חומצה קרבוקסילית משופרת על ידי חומצה גופרתית, אשר protonates את החמצן של קרבוניל. האלכוהול הוא נוקלאופיל התוקף את הפחמן של הקרבוניל כדי ליצור מתווך. לאחר מכן, המימן של האלכוהול מועבר הידרוקסיל סמוך. לאחר מכן הקרבוניל עובר רפורמה, ומחסל מולקולת מים. לבסוף, דה-פרוטונציה גורמת לאסתר ניטרלי.
במעבדה זו תבצעו תגובת אסטריפיקציה של פישר עם אלכוהול לא ידוע וחומצה קרבוקסילית ביחס מולארי של 3:1. לאחר מכן תזהו את האסתר באמצעות ריחו, תקבעו את התפוקה ותזהו את שני הריאגנטים הלא ידועים בהתבסס על מבנה האסתר.

אסטריפיקציה

<h4>אסטרים</h4>
המבנה של אסטר הוא קרבוניל עם קבוצת אלקיל או אריל (R) בצד אחד, וחמצן הקשור לקבוצת אלקיל או אריל אחרת (R') בצד השני, המיוצגת על ידי הנוסחה הכללית: RCOOR'. אסטרים יכולים להיווצר בדרך כלל על ידי תגובת אסטריפיקציה בין חומצה קרבוקסילית לאלכוהול. קבוצת ההידרוקסיל של החומצה הקרבוקסילית מוחלפת על ידי קבוצת אלקיל או אריל. אסטרים פשוטים, בעלי משקל מולקולרי נמוך וקבוצות פונקציונליות קטנות של R ו-R, הם בעלי ריחות וטעמים של פירות ופרחים.
החומצה הקרבוקסילית הפשוטה ביותר היא חומצה פורמית (HCOOH), כאשר האלכוהול הפשוט ביותר הוא מתנול. לפיכך, האסתר הפשוט ביותר שנוצר מהאסטריפיקציה של שתי מולקולות אלה הוא מתיל פורמט (HCOOCH3). פורמט מתיל נחשב לנגזרת של חומצה פורמית מכיוון שקבוצת OH מוחלפת על ידי קבוצת OCH3. ההבדלים המבניים בין פורמט מתיל לחומצה פורמית מכתיבים את ההבדל בתכונותיהם. הסיבה לכך היא שתכונות המולקולה תלויות במידה רבה בקבוצות R ו-R.
אסטרים הנמצאים בפירות ובפרחים ידועים כאסטרים פשוטים בשל המורכבות הנמוכה של המבנה שלהם בהשוואה לאסתרים אחרים. קבוצות האלקילים והארילים המצויות באסתרים אלה משפיעות מאוד על הניחוח שהם פולטים; לכן, תוספת של פחמן או קבוצה פונקציונלית אחרת יכולה להשפיע על הריח המיוצר על ידי אסטר. לדוגמה, פרופיל אצטט (C5H10O2) יש ריח של אגסים. עם זאת, בוטיל אצטט (C6H12O2), שיש לו רק פחמן אחד נוסף בשרשרת, מריח כמו תפוחים.
אסטרים ארוכי שרשרת, כלומר אלה עם שרשראות אלקיל ארוכות, נקראים חומצות שומן. חומצות שומן הן תרכובות ביולוגיות חשובות החיוניות לתהליכים ביולוגיים מסוימים. חומצות שומן הן גם צורה ביולוגית של אחסון אנרגיה. כאשר שלוש חומצות שומן מגיבות עם גליצרול, הן יוצרות טריגליצרידים — הצורה הנפוצה ביותר של חומצות שומן. טריגליצרידים יש משקל מולקולרי גבוה מאוד והוא יכול להיות מסועף מאוד. תפקידם ותכונותיהם תלויים באורכן ובסוגיהן של שרשראות אלקיל המשולבות במבנה שלהן. אחד השימושים התעשייתיים הנפוצים ביותר לטריגליצרידים הוא בייצור סבונים ודטרגנטים.
<h4>תגובת אסטריפיקציה</h4>
אסטרים נוצרים מתגובת אסטריפיקציה, כאשר אסטרים פשוטים נוצרים באמצעות אסטריפיקציה של פישר. תגובה זו ממירה חומצה קרבוקסילית ואלכוהול לאסתר עם מים כתוצר לוואי. אסטריפיקציה של פישר היא תגובה הפיכה שמתקדמת לאט מאוד. זרז חומצה, בדרך כלל בצורה של חומצה גופרתית, מתווסף כדי להגביר את קצב התגובה תוך שהוא מתנהג גם כסוכן מייבש.
מנגנון הפעולה של אסטריפיקציה של פישר מתחיל בכך שהחמצן הקרבוניל תוקף את החומצה הגופרתית ומפרק את קבוצת ה-OH שלה. זה מוביל חמצן קרבוניל טעון חיובי. כדי לייצב טוב יותר את המטען החיובי, זוג אלקטרונים אחד של הקשר הכפול הקרבוניל נדחף לחמצן הקרבוניל ובו זמנית יוצר מרכז פחמן דל אלקטרונים. לאחר מכן, קבוצת ההידרוקסי של האלכוהול פועלת כנוקלאופיל ותוקפת את הפחמן הדל באלקטרונים – האלקטרופיל – ויוצרת מתווך. לאחר מכן, קבוצת ההידרוקסיל הטעונה חיובית מהאלכוהול מפורקת על ידי קבוצת ההידרוקסיל של החומצה הקרבוקסילית, ומייצבת את אטום החמצן של האלכוהול. בשלב האחרון, החמצן הקרבוניל מתפרק על ידי הבסיס המצומד, וזוג האלקטרונים החופשיים מועבר לכיוון מרכז הקרבוניל בעוד קבוצת הקרבוקסיל הפרוטוני עוזבת כמולקולת מים.
מכיוון שתגובת האסטריפיקציה הפיכה, תערובת של 1:1 של החומצה הקרבוקסילית והאלכוהול תגיע לשיווי משקל עם תפוקה של כ-70% מהאסטר. עם זאת, כמו בכל תהליך שיווי משקל, התגובה יכולה להיות מונעת בכיוון אחד על ידי שינוי הריכוז, הלחץ, הטמפרטורה או הנפח של הריאגנטים. שינוי זה גורם לתגובה להסתגל לשיווי משקל חדש כדי לנטרל את השינוי, שהוא הבסיס לעקרון לה שטלייה.
כאשר ריכוז אחד המגיבים גדל, שיווי המשקל משתנה לכיוון שיקטין את ריכוזו. לכן, על ידי הגדלת הריכוז של מגיב אחד, שיווי המשקל מייצר יותר מהתוצר, ובכך מביא לתשואה גבוהה יותר של תוצר האסתר.
שיטה נפוצה אחת המשמשת במעבדות כימיה אורגנית היא לספק עודף של אחד הריאגנטים, בדרך כלל אלכוהול. כפי שהוזכר קודם לכן, אסטריפיקציה של פישר יכולה להשתמש בחומצה גופרתית כזרז. עם זאת, אחד התפקידים האחרים של חומצה גופרתית הוא לפעול כסוכן מייבש, בידוד מולקולות מים מן התגובה. יישום העיקרון של Le Chatelier מראה כי כאשר אחד המוצרים מוסר - במקרה זה, מים - התגובה נדחפת לייצור מוצר נוסף. זה מגדיל את התשואה של האסתר שנוצר.
<h4>הפניה</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). מבוא לכימיה אורגנית. נהר האוכף העליון, ניו ג'רזי: פרנטיס הול.</li>
</ol>

אסטרים
המבנה של אסטר הוא קרבוניל עם קבוצת אלקיל או אריל (R) בצד אחד, וחמצן קשור לקבוצה אלקיל או אריל אחרת (R') ...

Education

JoVE Lab Manual

Chemistry

כימיה

ester formation and everyday fragrances

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group.

Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl formate, the simplest ester from these two molecules. Methyl formate is a derivative of formic acid because the OH group is replaced by OCH3. Small changes in the R and R' groups can also change the properties and scent of an ester.

This is why similar esters can smell different. Propyl acetate has a pear-like scent, while butyl acetate smells like apples, even though the molecules differ by only one carbon. Long-chain esters are called fatty acids. They are important in biology and also serve as a form of energy storage.

When three fatty acids react with glycerol, they form a triglyceride. Triglycerides are the most common form of fatty acids and have a high molecular weight. They can also be highly branched. Their function and properties depend on the length and type of alkyl chains in their structure. Triglycerides are widely used in industry, including the production of soaps and detergents.

Simple esters are often made by Fischer esterification, which is a slow and reversible reaction. It converts a carboxylic acid and an alcohol into an ester and water. Sulfuric acid is commonly used as an acid catalyst. It speeds up the reaction and also acts as a dehydrating agent.

The reaction mechanism starts when the carbonyl oxygen interacts with sulfuric acid and becomes positively charged. The carbonyl double bond then shifts electron density toward the oxygen, leaving the carbonyl carbon more electron-poor. Next, the alcohol acts as a nucleophile and attacks that carbon, forming an intermediate. The alcohol oxygen is then deprotonated, and the carbonyl oxygen is finally deprotonated as water leaves.

Because Fischer esterification is reversible, a 1:1 mixture of the acid and alcohol reaches equilibrium at about 70% ester yield. The reaction can be pushed toward more ester by changing concentration, pressure, temperature, or volume. This follows Le Chatelier's principle, which says a system shifts to counter a change. In the lab, using excess alcohol is a common way to increase yield. Sulfuric acid also helps by removing water, and taking away this product drives the reaction to make more ester.

Ester Formation and Everyday Fragrances

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galvanic cells

Battery Power from Redox Reactions

Electrochemistry studies how chemical change and electrical energy are linked. In this branch of chemistry, electrons move from one species to another. That movement can either produce current or be driven by an applied current. The main reaction in electrochemistry is the oxidation-reduction, or redox, reaction. A redox reaction has two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. These changes also shift the oxidation state of each substance. The...

electrolytic cells

Electroplating with Electrolytic Cells

Electrochemistry links electrical energy with chemical change, and electrolytic cells show how electricity can drive a nonspontaneous reaction. In these reactions, electrons move from one species to another. The key chemistry is a redox reaction, or oxidation-reduction reaction, which happens in two half-reactions. Oxidation is the loss of electrons, and reduction is the gain of electrons. The substance that loses electrons is the reducing agent, and the substance that gains electrons is the...

proper lab notebook keeping

Recording a Reproducible Lab Experiment

Accurate lab notebook records are essential in science and organic chemistry labs. Without clear notes, descriptions, quantities, and observations, an experiment cannot be repeated or checked. Good record keeping supports reproducibility, which means other people can follow the same work and get similar results. A laboratory notebook is useful in school labs, research settings, and industry. It can also become a legal record when an idea, process, substance, or technique is patented and...

basic organic chemistry techniques

Organic Lab Glassware and Safe Handling

Organic chemistry labs use specific glassware, careful weighing steps, and controlled heating to keep reactions safe and accurate. Beakers and Erlenmeyer flasks are often used for mixing or holding solvents, but they are not meant for measuring volume unless only an approximate amount is needed. Volumetric glassware is used when a precise volume matters. This group includes graduated cylinders, volumetric pipettes, and volumetric flasks. A graduated cylinder is commonly used in the organic lab...

melting points

How Impurities Change Melting Points

Melting point helps identify an organic compound by showing the temperature where a solid turns into a liquid at 1 atmosphere of pressure. It is a physical property, like solubility, density, color, and electronegativity. Because the exact start of melting is hard to measure, the result is reported as a range. The lower end is when the first drops of liquid appear. The upper end is when the last solid has melted. Scientists compare this range with literature values to help identify a compound. <br...

boiling points

Boiling Point and Vapor Pressure

Boiling point and vapor pressure are key physical properties of a liquid. For a pure compound, the boiling point can help identify the substance. In experiments, the boiling point is usually recorded as a range because exact values are hard to measure and may differ by a few degrees from the literature value. Vapor pressure explains why a liquid boils. In a sealed container, some molecules at the liquid surface gain enough energy to escape into the gas phase. At the same time, some gas...

recrystallization

Purifying Crystals by Solubility

Purifying crystals by solubility is a key organic chemistry technique. Recrystallization uses differences in solubility to separate a desired solid product from starting materials, solvent, and impurities. It is one of the three standard purification methods, along with distillation and extraction. Solubility is the maximum amount of a substance that can dissolve in a fixed volume of solvent at a given temperature. Different solutes dissolve in different solvents, and their behavior can vary...

extraction

Separating Mixtures with Solvent Extraction

Solvent extraction is a common way to separate and isolate a target compound in organic chemistry. In this process, a solute moves from one phase to another so it can be separated from unreacted starting materials or impurities. Extraction is also useful when a product is dissolved in a reaction solvent that is hard to remove by evaporation, such as a solvent with a high boiling point. There are three main types of extraction. In solid-liquid extraction, the solute moves from a solid phase...

simple distillation

Separating Liquids by Boiling Point

Separating liquids by boiling point is the goal of distillation. A miscible mixture contains liquids that mix evenly, and it can be heated so that the more volatile liquid evaporates first. Volatility is a liquid’s tendency to vaporize, and boiling begins when bubbles form in the liquid phase. In a closed container, liquid and vapor can reach equilibrium, which means the rate of vaporization equals the rate of condensation. The pressure from the vapor above the liquid is called vapor pressure.

steam distillation

Steam Distillation and Low-Boiling Separation

Steam distillation is a separation method for temperature-sensitive organic compounds. It works best when the organic compound is immiscible in water, meaning the two liquids do not mix. The method helps remove the organic molecule from a non-volatile contaminant without using the higher temperatures needed for many other separations. In steam distillation, the immiscible mixture is heated until both water and the volatile organic compound distill together. The vapor rises to a condenser,...

thin-layer chromatography

TLC Separation by Polarity

Thin-layer chromatography (TLC) separates compounds in a mixture by polarity. It uses the same basic parts as other chromatography methods: a stationary phase, a mobile phase, and the solute. In TLC, the stationary phase is a thin coating on a plate instead of material packed into a column. The stationary phase in most TLC systems is polar silica gel, a form of silicon dioxide. Its surface has OH groups that can form hydrogen bonds. The sample is first spotted on a pencil start line with a...

column chromatography

Separating Mixtures by Polarity

Column chromatography separates compounds in an organic chemistry lab by using differences in physical properties. It is especially useful for microscale separations when less than 10 grams of material is available for analysis. The method can separate a mixture based on solubility, polarity, hydrophobicity, size, and charge. Any chromatography system has three main parts: the stationary phase, the mobile phase, and the sample mixture. In column chromatography, the stationary phase is usually...

hydrolysis of an ester

Soap Formation from Triglycerides

Triglycerides are lipids made of a glycerol backbone linked to three fatty acids. They are common in vegetable oils and animal fats. Plant lipids are the basis of vegetable oils, while animal lipids are used as lard or general sources of fats. A fatty acid has a long carbon chain, usually between 12 and 20 carbons, with a weak organic acid at one end. Some fatty acids contain double bonds. These are unsaturated fats. The double bond usually gives the chain a bent, cis shape. As a result,...

synthesis of luminol

Luminol Chemiluminescence in Forensics

Luminol chemiluminescence shows how a chemical reaction can produce light and help with blood detection. Chemical reactions may be endothermic or exothermic, depending on whether they absorb or release heat as reactants become products. The enthalpy of a reaction is the energy difference between reactants and products, or ΔH. A positive ΔH means the reaction is endothermic. A negative ΔH means it is exothermic. Many reactions do not happen in a single step. They can pass through intermediates...

esterification

Esters are organic compounds with a carbonyl group attached to an oxygen that connects to another alkyl or aryl group. Their general formula is RCOOR'. They are often made by reacting a carboxylic acid with an alcohol in an esterification reaction. In this process, the hydroxyl group of the acid is replaced by an alkyl or aryl group. Many simple esters have familiar fruit and flower smells because their structures are small and less complex. Formic acid and methanol can combine to form methyl...

identification of unknown aldehydes and ketones

identification-of-unknown-aldehydes-and-ketones

Carbonyl Tests for Aldehydes and Ketones

Aldehydes and ketones are carbonyl compounds, which means they contain a C=O functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon. Acetone is the simplest ketone, with two methyl groups. An aldehyde is similar, but it has at least one hydrogen attached to the carbonyl carbon. Formaldehyde is the simplest aldehyde, and acetaldehyde has one hydrogen and one methyl group. The carbonyl carbon in both aldehydes and ketones is electrophilic because the oxygen atom...

uv-vis spectroscopy of dyes

How Dyes Absorb Visible Light

Dyes absorb visible light because their molecular structure lets them interact with specific wavelengths. When light hits a substance, some light is absorbed and the rest is reflected or transmitted. The color we see depends on the wavelength that is reflected. A blue substance reflects blue light, around 430 to 480 nm, and absorbs the complementary orange region, around 590 to 630 nm. Compounds that do not absorb in the visible range appear colorless to the human eye. Light also has energy and...

identifying alcohols

Alcohol Tests for Primary, Secondary, and Tertiary

Alcohol tests can help sort alcohols by structure and reactivity. Alcohols are organic molecules with a hydroxyl group attached to an alkyl or aryl group, written as ROH. If the carbon with the hydroxyl group has one R group, the alcohol is primary. If it has two R groups, it is secondary. If it has three R groups, it is tertiary. Alcohols can also be aromatic when they contain a benzene ring. Phenol is the simplest aromatic alcohol. To identify an alcohol, chemists can use its chemical...

chemistry

Comprehensive, curriculum-focused videos for both instructors and students in introductory chemistry lab courses.

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Learn how carboxylic acids and alcohols form esters, why some smell fruity, and how Fischer esterification uses sulfuric acid to boost yield.

Ester Formation and Everyday Fragrances | JoVE K12

התכוננו ללמד את אסטריפיקציה עם מדריך מדריכים זה באורך 4 דקות. כולל שלבי הכנה מרכזיים עבור מעבדת Chemistry ב-JoVE Lab Manual.

הכנת מדריך עבור אסטריפיקציה ב-Chemistry - 10K+ צפיות | JoVE Lab Manual

עקבו אחר הנהלים של אסטריפיקציה שלב אחר שלב בסרטון פרוטוקול סטודנטים זה באורך 10 דקות. חלק מאוסף Chemistry ב-JoVE Lab Manual.

פרוטוקול סטודנטים עבור אסטריפיקציה ב-Chemistry - 20K+ צפיות | JoVE Lab Manual

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, ...

States of Matter

Solids, liquids, and gases are the three states of matter commonly found on Earth. A solid is rigid and possesses a definite shape. A liquid flows and ...

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 ...

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 ...

Differentiate between physical and chemical properties and physical and chemical changes of matter.

SC.912.P.8.1

physical-and-chemical-properties-of-matter

Physical and Chemical Properties of Matter

The characteristics that enable us to distinguish one substance from another are called properties.

Physical Properties of Matter

A physical property is ...

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

SC.912.P.8.2

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 ...

The Wave Nature of Light

The nature of light has been a subject of inquiry since antiquity. In the seventeenth century, Isaac Newton performed experiments with lenses and prisms ...

The Electromagnetic Spectrum

The electromagnetic spectrum consists of all the types of electromagnetic radiation arranged according to their frequency and wavelength. Each of the ...

Interference and Diffraction

Interference is a characteristic phenomenon exhibited by waves. When two electromagnetic waves interact with their peaks and troughs coinciding, a ...

Photoelectric Effect

When light of a particular wavelength strikes a metal surface, electrons are emitted. This is called the photoelectric effect. The minimum frequency of ...

The Bohr Model

Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded ...

Emission Spectra

When solids, liquids, or condensed gases are heated sufficiently, they radiate some of the excess energy as light. Photons produced in this manner have a ...

The de Broglie Wavelength

In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a ...

The Uncertainty Principle

Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that ...

The Quantum-Mechanical Model of an Atom

Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of ...

Explore the scientific theory of atoms (also known as atomic theory) by describing changes in the atomic model over time and why those changes were necessitated by experimental evidence.

SC.912.P.8.3

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 ...

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

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 ...

Atomic Number and Mass Number

The number of protons in the nucleus of an atom is its atomic number (Z). This is the defining trait of an element. Its value determines the identity of ...

Explore the scientific theory of atoms (also known as atomic theory) by describing the structure of atoms in terms of protons, neutrons and electrons, and differentiate among these particles in terms of their mass, electrical charges and locations within the atom.

SC.912.P.8.4

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 ...

Electron Configurations

Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest ...

Electronic Structure of Atoms


An atom comprises protons and neutrons, which are contained inside the dense, central&#160;core called the nucleus, with electrons present around the ...

Electron Behavior

Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside in ...

Relate properties of atoms and their position in the periodic table to the arrangement of their electrons.

SC.912.P.8.5

A. A working definition of matter is that it takes up space, has mass, and has measurable properties. Matter is comprised of atomic, subatomic, and elementary particles.

B. Electrons are key to defining chemical and some physical properties, reactivity, and molecular structures. Repeating (periodic) patterns of physical and chemical properties occur among elements that define groups of elements with similar properties. The periodic table displays the repeating patterns, which are related to the atom's outermost electrons. Atoms bond with each other to form compounds.

C. In a chemical reaction, one or more reactants are transformed into one or more new products. Many factors shape the nature of products and the rates of reaction. 

D. Carbon-based compounds are building-blocks of known life forms on earth and numerous useful natural and synthetic products.

Ester Formation and Everyday Fragrances

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