Name: average atomic mass and isotopes
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 1 min 52 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.2.1

Atomic Mass

Tek bir atomun kütlesi çok küçük olduğundan, kütleyi gram veya kilogram olarak ölçmek pratik değildir. Atomların ve moleküllerin kütlesi, Dalton, kısaca Da, veya atomik kütle birimi, kısaca akb veya bazen sadece u olarak adlandırılan birimlerle ölçülür. Atomik kütle birimindeki bir atomun kütlesi yaklaşık olarak proton sayısı ve nötron sayısının toplamına eşittir;ancak, çoğu elementin doğal olarak oluşan birkaç izotopu vardır.Bu izotopların her biri farklı sayıda nötron ve dolayısıyla farklı bir kütleye sahiptir. Her element için, ortalama kütlesi, elementin izotoplarının kütleleri toplanarak hesaplanır, her biri yeryüzündeki doğal fraksiyonel bolluğu ile çarpılır. Bir elementin çeşitli izotoplarının kütlesi ve nispi bolluğu, kütle spektrometresi kullanılarak belirlenebilir.İzotoplar kütle ile ayrılır ve bir numunenin kütle spektrumu izotopların nispi bolluğunu gösterir. Bu değerler, periyodik tabloda görünen ortalama atomik kütleyi hesaplamak için kullanılır. Temsili bir bor numunesinin kütle spektrumu, bu numunenin 19, 9'unun 10, 0129 akb kütleli bor-10 olduğunu göstermektedir.Gerisi ise 11, 0093 akb kütleli bor-11'dir. Bor-10 ve bor-11'in kütlelerinin her biri, nispi bollukları ile çarpılır, bor-10 için 100'de 19, 9 ve bor-11 için 100'de 80, 1. Bu değerler daha sonra borun ortalama atomik kütlesini bulmak için toplanır.

atomik kütle

Atomlar ve onları oluşturan proton, nötron ve elektronlar son derece küçüktür. Örneğin bir karbon atomunun kütlesi 2 × 10−23 g'dan daha azdır. Atomlar gibi küçük nesnelerin özelliklerini tanımlarken, atomik kütle birimi (amu) gibi uygun küçük ölçü birimlerini kullanırız. Amu başlangıçta en hafif element olan hidrojene ve daha sonra oksijene göre tanımlandı. 1961'den bu yana, atomları tam olarak 12 amu kütlelerine atanan en bol karbon izotopu referans alınarak tanımlanmıştır. Böylece 1 amu tam olarak bir karbon-12 atomunun kütlesinin 1/12'sine eşittir: 1 amu = 1,6605 × 10−24 g. Dalton (Da) ve birleşik atomik kütle birimi (u), amu'ya eşdeğer alternatif birimlerdir.
 
 Her proton ve her nötron bir atomun kütlesine yaklaşık bir amu katkıda bulunduğundan ve her elektron çok daha az katkıda bulunduğundan, tek bir atomun atom kütlesi yaklaşık olarak kütle sayısına eşittir (atomdaki proton ve nötronların tam sayı toplamı). Örneğin, tek bir azot atomunun kütle numarası 14'tür (7 proton + 7 nötron). Bununla birlikte, çoğu elementin atomlarının ortalama kütleleri tam sayı değildir, çünkü çoğu element doğal olarak iki veya daha fazla izotop karışımı olarak bulunur. İzotoplar, aynı proton sayısına sahip aynı elementin atomlarıdır, ancak farklı sayıda nötron içerirler. Periyodik tabloda gösterilen veya atomik kütleler tablosunda listelenen bir elementin kütlesi, bu elementin doğal olarak oluşan bir örneğinde bulunan tüm izotopların ağırlıklı ortalama kütlesidir. Ortalama kütle, her bir izotopun kütlesinin nispi bolluğu ile çarpılan toplamına eşittir.
 
 <img alt=""Eq1"" src=""https://www.jovecore.com/CDNSource/lessons/807/807_Equations-01.png"" style=""height: 40px;"" />
 
 Örneğin, klor elementi (atom numarası 17) iki izotoptan oluşur: 35Cl ve klorin 37Cl. Tüm klor atomlarının yaklaşık %75,78'i 34,969 amu kütleli 35Cl'dir ve kalan %24,22'si 36,966 amu kütleli 37Cl'dir. Klor için ortalama atom kütlesi şu şekilde hesaplanır:
 
 <img alt=""Eq1"" src=""https://www.jovecore.com/CDNSource/lessons/807/807_Equations-02.png"" style=""height: 40px;"" />
 
 Tek bir klor atomunun tam olarak 35,45 amu ağırlığında olmadığını anlamak önemlidir; bu değer tüm klor atomlarının ortalama kütlesidir ve bireysel klor atomları yaklaşık 35 amu veya 37 amu ağırlığındadır. Ayrıca, doğal olarak oluşan klor, 37Cl atomlarından daha fazla 35Cl atomu içerdiğinden, ağırlıklı ortalama klor kütlesi 35 amu'ya 37 amu'dan daha yakındır.
 
 İzotopların oluşumu ve doğal bolluğu, kütle spektrometresi adı verilen bir cihaz kullanılarak deneysel olarak belirlenebilir. Kütle spektrometresi (MS), bir malzeme örneğindeki maddeleri analiz etmek ve tanımlamaya yardımcı olmak için kimya, adli tıp, tıp, çevre bilimleri ve diğer birçok alanda yaygın olarak kullanılmaktadır. Tipik bir kütle spektrometresinde, numune buharlaştırılır ve numunenin atomlarının veya moleküllerinin tipik olarak bir veya daha fazla elektron kaybederek elektrik yüklü olmasına neden olan yüksek enerjili bir elektron ışınına maruz bırakılır. Bu katyonlar daha sonra her katyonun yolunu hem kütlesine hem de yüküne bağlı olan ölçüde saptıran değişken bir manyetik alandan geçer. Son olarak, iyonlar tespit edilir ve kütle-yük oranlarına, bir kütle spektrumuna karşı üretilen nispi iyon sayısının bir grafiği yapılır. Bir kütle spektrumundaki her dikey özelliğin veya zirvenin yüksekliği, belirtilen kütle-yük oranına sahip katyonların fraksiyonu ile orantılıdır. Modern atom teorisinin gelişimi sırasında ilk kullanımından bu yana, MS geniş bir uygulama yelpazesinde kimyasal analiz için güçlü bir araç haline gelmiştir.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href=""https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism"">Openstax Chemistry 2e, Section 2.3: Atomic Structure and Symbolism.</a>

Atomik Kütle

Atomlar - ve onları oluşturan protonlar, nötronlar ve elektronlar - son derece küçüktür. Örneğin, bir karbon atomu 2 ...

Education

JoVE Core

Kimya

Atoms and Elements

Atomlar ve Elementler

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

average atomic mass and isotopes

Average atomic mass explains why many elements on the periodic table have decimal values. Atoms are extremely small, so scientists use the atomic mass unit, or amu, to measure them. A carbon atom weighs less than 2 × 10−23 g, and the amu is defined from carbon-12. One amu is exactly 1/12 the mass of one carbon-12 atom, which is 1.6605 × 10−24 g. The dalton (Da) and the unified atomic mass unit (u) mean the same thing as the amu.

For a single atom, atomic mass is usually close to its mass number. The mass number is the total of protons and neutrons in the atom. Each proton and neutron contributes about 1 amu, while each electron adds far less. For example, a nitrogen atom has a mass number of 14 because it has 7 protons and 7 neutrons.

Most elements do not have a whole-number atomic mass because they exist as mixtures of isotopes. Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons. The atomic mass listed for an element in the periodic table is a weighted average of the masses of all naturally occurring isotopes. This average is found by multiplying each isotope’s mass by its fractional abundance and then adding the results.

Chlorine is a good example. It has two isotopes, chlorine-35 and chlorine-37. About 75.78% of chlorine atoms are chlorine-35 with a mass of 34.969 amu, and 24.22% are chlorine-37 with a mass of 36.966 amu. The average atomic mass of chlorine is 35.45 amu. No single chlorine atom has exactly that mass. Individual chlorine atoms are closer to 35 amu or 37 amu, depending on the isotope.

Scientists can measure isotopes and their natural abundance with a mass spectrometer. Mass spectrometry, or MS, is used in chemistry, forensics, medicine, environmental science, and other fields to identify substances in a sample. In a mass spectrometer, the sample is vaporized and hit with a high-energy electron beam. This makes the atoms or molecules become charged, usually by losing one or more electrons. The cations then move through a magnetic field, which bends their paths based on mass and charge. The detector records them and creates a mass spectrum, a graph of ion count versus mass-to-charge ratio. Each peak shows how many ions have a given mass-to-charge ratio. Since its early use in modern atomic theory, MS has become a powerful tool for chemical analysis.

Average Atomic Mass and Isotopes

the atomic theory of matter

Dalton’s Laws and Early Atomic Ideas

Dalton’s atomic theory explains matter with atoms, elements, and compounds. It also shows how chemical changes follow simple laws. This idea gave chemistry a microscopic model for what can be seen in the lab. The earliest recorded ideas about matter came from ancient Greek philosophers. Leucippus and Democritus said all matter was made of tiny, finite particles called atomos, meaning “indivisible.” Aristotle and others later argued that matter was made from four elements: fire, earth, air, and...

subatomic particles

Atomic Structure: Protons, Neutrons, and Electrons

Atomic structure is built from three subatomic particles: protons, neutrons, and electrons. Atoms make up all matter, and these particles explain an atom’s mass and charge. The electron was first identified at the end of the 19th century by J.J. Thomson. He used a cathode ray tube, a sealed glass tube with almost all the air removed and two metal electrodes. When high voltage was applied, a visible beam called a cathode ray formed. The beam bent toward positive charge and away from negative...

elements: chemical symbols and isotopes

Reading Element Symbols and Isotope Notation

Chemical symbols and isotope notation help identify elements and their atoms. A chemical symbol is an abbreviation for an element or a single atom of that element. Mercury, for example, is written as Hg. The same symbol can point to one atom in the microscopic domain or to many atoms of the element in a container or sample. Many symbols come from the element’s common English name. Others come from Latin, Greek, or German names. Aluminum uses Al, while iron uses Fe from the Latin word Ferrum.

ions and ionic charges

Predicting Ion Charges on the Periodic Table

Ion charges can often be predicted from an element’s position on the periodic table. In chemical reactions, the nucleus stays unchanged, but electrons may be transferred, lost, or shared. When atoms gain or lose electrons during compound formation, they become ions, which are electrically charged particles. A positive ion is called a cation. A cation has more protons than electrons because it lost electrons. A negative ion is called an anion. An anion has more electrons than protons because it...

the periodic table

Periodic Table Patterns and Element Groups

The periodic table organizes elements by repeating patterns in their properties. Chemists first noticed that some elements behaved alike, so they grouped them by chemical behavior. Lithium, sodium, and potassium are one example. They are shiny and conduct heat and electricity well. Calcium, strontium, and barium form another group with similar physical and chemical properties. Yet these two groups are not the same. The lithium group is much more reactive, and its elements form oxygen compounds...

atomic mass

Average atomic mass explains why many elements on the periodic table have decimal values. Atoms are extremely small, so scientists use the atomic mass unit, or amu, to measure them. A carbon atom weighs less than 2 × 10−23 g, and the amu is defined from carbon-12. One amu is exactly 1/12 the mass of one carbon-12 atom, which is 1.6605 × 10−24 g. The dalton (Da) and the unified atomic mass unit (u) mean the same thing as the amu. For a single atom, atomic mass is usually close to its mass...

molar mass

Mole, Mass, and Avogadro’s Number

The mole links mass and the number of particles in a substance. It gives chemists a standard way to count atoms and molecules in samples that are far too small to see. It also helps show why substances with the same kinds of atoms can still have very different properties, like water, H2O, and hydrogen peroxide, H2O2. The mole is an amount unit, like a pair or a dozen. One mole contains 6.02214076 × 10^23 discrete entities, such as atoms or molecules. This number is usually rounded to 6.022 ×...

key terms and concepts

Learn how isotopes, fractional abundance, and mass spectrometry explain average atomic mass values on the periodic table for high school chemistry.

Average Atomic Mass and Isotopes | JoVE K12

chemistry

JoVE Core Kimya, özlü ve kolay anlaşılır animasyon video derslerini kullanarak genel kimya kavramlarına hayat veriyor. Ek olarak, bilim insanı uygulama videolarımız ile klasik ve orijinal araştırma deneylerini dünya çapında günümüz laboratuvarlarında görselleştiriyoruz.

PS.Chm.4.3

PS.Chm.4.4

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Physical Science

Study Of Matter

Atoms

Structure And Properties Of Matter

Quantifying matter

Physical Geology

Minerals

Atoms and elements

Virginia  Standards of Learning

HIgh School

CH.2

CH.2.a

CH.4

CH.4.a

PS.4

PS.4.a

Texas Essential Knowledge and Skills

High School

CHEM.8

CHEM.8.A

CHEM.11

CHEM.11.E

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.1

9-12.PS.3.4.d

Next Generation Science Standards

Earth and Space Science

Earth’s Place in the Universe

HS-ESS1-3

Florida Department of Education

SC.912.P.8

SC.912.P.8.4

Chemistry and Physics

IPC.7

IPC.7.A

Georgia Standards of Excellence

SC1.

Isotopes and Atomic Mass

Scientific Laws and Theories

Scientific Laws

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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 ...

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Classifying Matter by Composition

Matter: Pure Substances and Mixtures
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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

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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

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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

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Radioactive Decay and Radiometric Dating

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Nuclear Fission

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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

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Nuclear Transmutation

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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

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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

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The Aufbau Principle and Hund's Rule

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Electron Configuration of Multielectron Atoms

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Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

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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 ...

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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.

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

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Ionic Radii

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Ionization Energy

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Electron Affinity

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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

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Lewis Symbols and the Octet Rule

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Ionic Bonding and Electron Transfer

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The Born-Haber Cycle

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Covalent Bonding and Lewis Structures

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Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

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Lewis Structures of Molecular Compounds and Polyatomic Ions

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	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

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Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

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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

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Molecular Comparison of Gases, Liquids, and Solids

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Intermolecular vs Intramolecular Forces

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Intermolecular Forces

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Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

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Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

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

PS.Chm.3.2

Analyze the structure of atoms and isotopes.

Average Atomic Mass and Isotopes

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