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

에스테르는 과일 향이나 꽃 향을 가질 수 있는 유기 분자의 한 종류입니다. 에스테르의 구조는 한쪽 면에 알킬기 또는 아릴기가 있고 다른 면에 다른 알킬기 또는 아릴기에 산소가 결합된 카르보닐기입니다.
알킬 또는 아릴 그룹에 따라서, 에스테르는 많은 다른 특성을 가질 수 있습니다. 예를 들어, 글리세롤과 긴 알킬 사슬을 가진 카르복실산인 3개의 지방산의 반응은 3개의 에스테르 그룹이 있는 트리글리세리드를 생성합니다. 지방산에서 나오는 긴 알킬 사슬은 트리글리세리드에 매우 높은 분자량을 부여합니다. 대조적으로, 단순 에스테르는 분자량이 낮고 작용기가 작습니다.
과일과 꽃의 냄새와 풍미는 단순한 에스테르에 기인합니다. 단순한 에스테르의 구조에 대한 작은 변화조차도 향기에 큰 영향을 미칩니다. 예를 들어, 하이드록실기를 아민으로 변경하면 이 에스테르의 향이 윈터그린에서 포도로 바뀝니다. 마찬가지로 프로필 아세테이트는 배 냄새가 나는 반면, 사슬에 탄소가 하나만 더 있는 부틸 아세테이트는 사과 냄새가 납니다.
에스테르를 만드는 일반적인 방법 중 하나는 피셔 에스테르화(Fischer esterification)로, 카르복실산과 알코올이 산 촉매의 존재 하에서 반응하여 에스테르와 물을 형성하는 것입니다. R기와 카르보닐기는 카르복실산에서 유래하고, R'을 함유한 알콕시 또는 아릴옥시기는 알코올에서 유래합니다. 이 에스테르화 반응은 가역적입니다. 카르복실산과 알코올의 1 대 1 혼합물로, 에스테르의 약 70 % 수율로 평형에 도달하는 경향이 있습니다.
그러나 Le Chatelier의 원리를 통해 그 이상으로 에스테르의 수율을 높일 수 있습니다. 르 샤틀리에(Le Chatelier)의 원리에 따르면 농도, 압력, 온도 또는 부피의 변화를 받는 화학적 평형 상태의 모든 시스템은 그 변화에 대응하는 새로운 평형 상태로 조정됩니다.
따라서 가역적 반응에서 반응물 중 하나의 농도를 증가시키면 평형은 농도를 감소시키는 방향으로 이동합니다. 그 결과 평형 상태에서 에스테르 생성물의 수율이 높아집니다. 따라서, 우리는 카르복실산과 알코올의 3:1 또는 1:3 몰 비율을 사용하여 에스테르화 수율을 향상시킬 수 있습니다.
이 실험에서는 과량의 알코올과 황산을 촉매로 사용하여 피셔 에스테르화를 수행합니다. 이 반응에서, 카르복실산 반응성은 카르보닐의 산소를 양성자화하는 황산에 의해 강화됩니다. 알코올은 카르보닐의 탄소를 공격하여 중간체를 형성하는 친핵물질입니다. 다음으로, 알코올의 수소는 근처의 수산기로 전달됩니다. 그런 다음 카르보닐은 재형성되어 물 분자를 제거합니다. 마지막으로, 탈양성자화는 중성 에스테르를 생성합니다.
이 실험실에서는 알려지지 않은 알코올과 카르복실산을 3:1의 몰비로 Fischer 에스테르화 반응을 수행합니다. 그런 다음 냄새를 사용하여 에스테르를 식별하고, 수율을 결정하고, 에스테르의 구조를 기반으로 두 개의 알려지지 않은 시약을 식별합니다.

에스테르화

<h4>에스테르</h4>
에스테르의 구조는 한쪽 면에 알킬기 또는 아릴기(R)를 갖는 카르보닐기이고, 다른 면에는 다른 알킬기 또는 아릴기(R')에 산소가 결합되어 있으며, RCOOR'라는 일반 화학식으로 표시됩니다. 에스테르는 일반적으로 카르복실산과 알코올 사이의 에스테르화 반응에 의해 유도될 수 있습니다. 카르복실산의 수산기는 알킬기 또는 아릴기로 대체됩니다. 저분자량과 작은 R 및 R '작용기를 갖는 단순 에스테르는 과일과 꽃의 냄새와 풍미를 가지고 있습니다.
가장 간단한 카르복실산은 포름산(HCOOH)이며 가장 간단한 알코올은 메탄올입니다. 따라서이 두 분자의 에스테르 화로 형성된 가장 간단한 에스테르는 포름산 메틸 (HCOOCH3 )입니다. 포름산메틸은 OH 그룹이 OCH3 그룹으로 대체되기 때문에 포름산의 유도체로 간주됩니다. 포름산메틸과 포름산의 구조적 차이는 그 특성의 차이를 결정합니다. 이것은 분자의 특성이 R과 R' 그룹에 크게 의존하기 때문입니다.
과일과 꽃에서 발견되는 에스테르는 다른 에스테르에 비해 구조의 복잡성이 낮기 때문에 단순 에스테르로 알려져 있습니다. 이 에스테르에서 발견되는 알킬 및 아릴 그룹은 그들이 방출하는 향기에 큰 영향을 미칩니다. 따라서 탄소 또는 다른 작용기의 첨가는 에스테르에서 생성되는 향에 영향을 미칠 수 있습니다. 예를 들어, 프로필 아세테이트 (C5H10O2 )는 배의 향기가 있습니다. 그러나 사슬에 탄소가 하나만 더 있는 부틸 아세테이트(C6H12O2 )는 사과 냄새가 납니다.
긴 알킬 사슬을 가진 것을 의미하는 장쇄 에스테르는 지방산이라고 합니다. 지방산은 특정 생물학적 과정에 필수적인 중요한 생물학적 화합물입니다. 지방산은 또한 에너지 저장의 생물학적 형태입니다. 세 가지 지방산이 글리세롤과 반응하면 가장 일반적인 형태의 지방산인 트리글리세리드를 형성합니다. 트리글리세리드는 분자량이 매우 높으며 분지가 많을 수 있습니다. 그들의 기능과 특성은 구조에 통합된 알킬 사슬의 길이와 유형에 따라 다릅니다. 트리글리세리드의 가장 일반적인 산업 용도 중 하나는 비누 및 세제 생산입니다.
<h4>에스테르화 반응</h4>
에스테르는 에스테르화 반응으로 형성되며, 단순 에스테르는 피셔 에스테르화를 통해 형성됩니다. 이 반응은 카르복실산과 알코올을 부산물로 물을 함유한 에스테르로 전환합니다. 피셔 에스테르화(Fisher esterification)는 매우 천천히 진행되는 가역적 반응입니다. 일반적으로 황산 형태의 산 촉매를 첨가하여 반응 속도를 높이는 동시에 탈수제 역할도 합니다.
피셔 에스테르화(Fisher esterification)를 위한 작용 메커니즘은 카르보닐 산소가 황산을 공격하고 OH 그룹을 탈양성자화함으로써 시작됩니다. 이것은 양전하를 띤 카르보닐 산소로 이어집니다. 양전하를 더 잘 안정화하기 위해 카르보닐 이중 결합의 한 전자 쌍을 카르보닐 산소로 밀어 넣는 동시에 전자가 부족한 탄소 중심을 생성합니다. 다음으로, 알코올의 하이드록시 그룹은 친핵체로 작용하여 전자가 부족한 탄소(친전자성)를 공격하여 중간체를 형성합니다. 그런 다음, 알코올의 양전하를 띤 수산기는 카르복실산의 수산기에 의해 탈양성자화되어 알코올의 산소 원자를 안정화합니다. 마지막 단계에서 카르보닐 산소는 공액 염기에 의해 탈양성자화되고 자유 전자쌍은 카르보닐 중심을 향해 이동하는 반면 양성자화된 카르복실기는 물 분자로 남습니다.
에스테르 화 반응은 가역적이기 때문에 카르 복실 산과 알코올의 1 : 1 혼합물은 에스테르의 약 70 % 수율로 평형에 도달합니다. 그러나 모든 평형 과정과 마찬가지로 반응은 시약의 농도, 압력, 온도 또는 부피를 변경하여 한 방향으로 구동될 수 있습니다. 이 변화는 반응이 변화에 대응하기 위해 새로운 평형에 적응하도록 하며, 이것이 르 샤틀리에 원칙의 기초입니다.
반응물 중 하나의 농도가 증가하면 평형은 농도를 감소시키는 방향으로 이동합니다. 따라서, 하나의 반응물의 농도를 증가시킴으로써, 평형은 더 많은 생성물을 생성하며, 그로 인해 에스테르 생성물의 수율이 높아집니다.
유기 화학 실험실에서 사용되는 일반적인 방법 중 하나는 시약 중 하나(일반적으로 알코올)를 과도하게 제공하는 것입니다. 앞서 언급했듯이 Fisher 에스테르화는 황산을 촉매로 사용할 수 있습니다. 그러나 황산의 다른 기능 중 하나는 탈수제로 작용하여 물 분자를 반응에서 멀리 격리하는 것입니다. 르 샤틀리에(Le Chatelier)의 법칙을 적용하면 제품 중 하나(이 경우 물)가 제거되면 반응이 더 많은 제품을 만들도록 강요된다는 것을 보여줍니다. 이것은 형성된 에스테르의 수율을 증가시킨다.
<h4>참조</h4>
<ol>
	<li style="font-size:17px">Streitwieser, A., Heathcock, C.H., Kosower, E.M. (1998). 유기 화학 소개. 어퍼 새들 리버, 뉴저지 : 프렌티스 홀.</li>
</ol>

에스테르
에스테르의 구조는 한쪽 면에 알킬기 또는 아릴기(R)가 있고 다른 면에 산소가 결합된 카르보닐기(R')입니다.

Education

교육

JoVE Lab Manual

Chemistry

화학

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.

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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

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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

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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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