Name: electron affinity trends on the periodic table
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 3 min 7 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.2.2

Electron Affinity

Gaz halindeki bir atoma bir elektron eklendiğinde, elektron afinitesi adı verilen enerjide bir değişiklik gözlenir. Elektron afinitesi, bir atom tarafından elektron kazanma kolaylığının ölçüsüdür. Örneğin, klorun elektron ilgisi mol başına 348, 6 kilojul'dur.Eksi işareti, bunun ekzotermik bir değişiklik olduğunu gösterir. Bununla birlikte, argon, bir argon anyonunun oluşumunun enerji gerektirdiğini gösteren pozitif bir elektron afinitesine sahiptir. Genel olarak, bir atom ile eklenen bir elektron arasındaki çekim ne kadar büyükse, elektron ilgisi o kadar negatif olur.İyonlaşma enerjilerine benzer elektron afiniteleri, periyodik tablodaki eğilimleri gösterir. Grup 1'den aşağıya inerken, elektronlar daha yüksek temel kuantum sayılarını işgal ettikçe atom boyutu artar. Bu nedenle, kazanılan elektronlar, daha az negatif elektron ilgisine yol açan daha az nükleer çekime maruz kalırlar.Ancak istisnalar vardır. Halojenlerde klor, flordan daha negatif bir elektron afinite değerine sahiptir. Ama neden?Flor, halojenlerin en küçük atomudur ve gelen bir elektron, halihazırda mevcut olan elektronlar tarafından güçlü bir şekilde itilir. Ancak klorür anyonunda yeni elektron üçüncü kabuğa eklenir ve daha fazla yer kaplar. Bu, elektron-elektron itmelerini azaltır ve elektron kazanma ihtimalini artırır.Genel olarak, bir periyod boyunca elektron ilgileri daha negatif hale gelir. Halojenler, gelen elektron asal gaz konfigürasyonlarının elde edilmesine yardımcı olduğundan, en negatif elektron ilgisine sahiptir. Buna karşılık, soy gazların tamamen dolu bir kabuğu vardır.Gelen elektron, enerji açısından elverişsiz olan yüksek temel enerji seviyesinde barındırılmalıdır. Dolayısıyla, bu elementler için elektron ilgisi pozitiftir. Grup 2'de istisnalar mevcuttur.Elektron konfigürasyonu, gelen elektronun daha yüksek enerjili bir alt kabuğa girmesi gerektiğini gösterir. Bu nedenle, elektron afinite değerleri ya pozitiftir ya da daha az ekzotermiktir. İlginçtir ki, grup 15'in negatif elektron ilgisi grup 14'e göre daha azdır.Fosfor ve silikonu karşılaştıralım. Silikondan farklı olarak, fosforun yarı dolu bir p-alt kabuğu vardır ve gelen elektronun halihazırda p-yörüngesinde bulunan bir elektronla eşleştirilmesi gerekir. Bu, elektron-elektron itmelerini artıracaktır ve bu nedenle, silikona kıyasla daha az negatif elektron afinitesine de yansıyan enerjik olarak elverişsiz bir süreçtir.

elektron afinitesi

Elektron afinitesi (EA), bir anyon (negatif iyon) oluşturmak için bir gaz halindeki atoma bir elektron eklemek için enerji değişimidir.
 
 <img alt="Eq1" src="https://www.jovecore.com/CDNSource/lessons/1050/1050_Equations-01.png" style="height: 40px;" />
 
 Bu işlem, elemente bağlı olarak endotermik veya ekzotermik olabilir. Bu elementlerin çoğu negatif EA değerlerine sahiptir, bu da gaz halindeki atom bir elektron kabul ettiğinde enerjinin açığa çıktığı anlamına gelir. Bununla birlikte, bazı elementler için, atomun negatif yüklü hale gelmesi için enerji gerekir ve EA'larının değeri pozitiftir. İyonlaşma enerjisinde olduğu gibi, sonraki EA değerleri daha fazla yüklü iyonların oluşturulmasıyla ilişkilidir. İkinci EA, –2 iyon oluşturmak için bir anyona bir elektron eklenmesi ile ilişkili enerjidir ve bu böyle devam eder.
 
 Tahmin edileceği gibi, atomların etkili nükleer yükü arttıkça, bir dizi atom boyunca bir elektron eklemek daha kolay hale gelir. Bir periyot boyunca soldan sağa gittiğimizde, EA'lar daha negatif olma eğilimindedir. Grup 2 (2A), grup 15 (5A) ve grup 18 (8A) elementleri arasında bulunan istisnalar, bu grupların elektronik yapısına dayanılarak anlaşılabilir. Soy gazlar, grup 18 (8A), tamamen dolu bir kabuğa sahiptir ve gelen elektronun, yapılması daha zor olan daha yüksek bir n seviyesine eklenmesi gerekir. Grup 2 (2A), doldurulmuş bir ns alt kabuğuna sahiptir ve bu nedenle eklenen bir sonraki elektron daha yüksek enerjili np, gider, bu nedenle, yine, gözlemlenen EA değeri eğilimin tahmin edeceği gibi değildir. Son olarak, grup 15 (5A) yarı dolu np alt kabuğuna sahiptir ve bir sonraki elektron mevcut bir np elektronu ile eşleştirilmelidir. Tüm bu durumlarda, elektron konfigürasyonunun başlangıçtaki göreceli kararlılığı, EA'daki eğilimi bozar.
 
 Her grubun tepesindeki atomun en negatif EA'ya sahip olması beklenebilir; ilk iyonlaşma potansiyelleri, bu atomların en büyük etkili nükleer yüklere sahip olduğunu göstermektedir. Bununla birlikte, bir grup aşağı doğru ilerlerken, gruptaki ikinci elementin en negatif EA'ya sahip olduğunu görürüz. Bu, n = 2 kabuğunun küçük boyutuna ve ortaya çıkan büyük elektron-elektron itmelerine bağlanabilir. Örneğin, EA değeri –348 kJ/mol olan klor, periyodik tablodaki herhangi bir element arasından en yüksek değere sahiptir. Florun EA'sı –322 kJ/mol'dür. Bir florür anyonu (F–) oluşturmak için bir flor atomuna bir elektron eklediğimizde, n = 2 kabuğuna bir elektron ekleriz. Elektron çekirdeğe çekilir, ancak bu küçük değerlik kabuğunda zaten mevcut olan diğer elektronlardan da önemli bir itme vardır. Klor atomu, değerlik kabuğunda aynı elektron konfigürasyonuna sahiptir, ancak giren elektron n = 3 kabuğuna girdiğinden, önemli ölçüde daha geniş bir alan kaplar ve elektron-elektron itmeleri azalır. Giren elektron o kadar fazla itme yaşamaz ve klor atomu ek bir elektronu daha kolay kabul eder, bu da daha negatif bir EA ile sonuçlanır.
 
 Bu metin bu kaynaktan uyarlanmıştır: <a href="https://openstax.org/books/chemistry-2e/pages/6-5-periodic-variations-in-element-properties">OpenStax Chemistry 2e, Section 6.5: Periodic Variations in Element Properties.</a>

Elektron Afinitesi

Elektron ilgisi (EA), bir anyon (negatif iyon) oluşturmak için gaz halindeki bir atoma bir elektron eklemek için kullanılan enerji değişimidir.

Bu işlem şunlardan biri olabilir...

Education

JoVE Core

Kimya

Periodic Properties of the Elements

Elementlerin Periyodik Özellikleri

KEY TERMS AND CONCEPTS

TEMEL TERİMLER VE KAVRAMLAR

electron affinity trends on the periodic table

Electron affinity is the energy change that happens when a gaseous atom gains an electron and becomes a negative ion, or anion. For many elements, this process releases energy, so the electron affinity value is negative. For some elements, energy must be added instead, so the value is positive.

Electron affinity also applies when more than one electron is added. The second electron affinity is the energy change for adding an electron to an anion to make a 2− ion. Later electron affinities follow the same idea for ions with even more charge.

Across a period, electron affinity usually becomes more negative from left to right. This pattern fits the increase in effective nuclear charge, which makes it easier for atoms to attract an added electron. Some groups do not follow the trend well, though. Group 2 has a filled ns subshell, group 15 has a half-filled np subshell, and group 18 has a full shell, so the next electron must enter a less favorable state.

These exceptions are linked to electron arrangement and stability. Noble gases must place the new electron in a higher n level. Group 2 elements add the electron to a higher-energy np orbital. Group 15 elements must pair the new electron with one already in the np subshell. In each case, the stable starting configuration changes the expected electron affinity.

Down a group, the most negative electron affinity is often found in the second element rather than the top one. The small size of the n = 2 shell can create stronger electron-electron repulsions. That is why chlorine has a more negative electron affinity than fluorine. Chlorine’s value is −348 kJ/mol, while fluorine’s is −322 kJ/mol. When fluorine gains an electron, the added electron enters the small n = 2 shell. In chlorine, the electron goes into the larger n = 3 shell, so repulsion is lower and the atom accepts the electron more readily.

Electron Affinity Trends on the Periodic Table

electron-affinity-trends-on-the-periodic-table

periodic classification of the elements

How Valence Electrons Shape the Periodic Table

The periodic table organizes elements by increasing atomic number, and it also shows why elements in the same group behave alike. As the electron configurations are placed into the table, a repeating pattern appears in the outer shells of atoms. These outer electrons are called valence electrons, and they play the biggest role in chemical reactions. They are the highest-energy electrons in an atom, so they are easier to lose or share than core electrons. Valence electrons also help determine...

ionization energy

Ionization Energy Trends in the Periodic Table

Ionization energy is the energy needed to remove an electron from a gaseous atom or ion in its ground state. The first ionization energy, or IE1, removes the most loosely bound electron and forms a 1+ cation. The second ionization energy, IE2, removes the next electron, and each later ionization energy removes another electron from the atom or ion. Ionization always requires energy, so these processes are endothermic. That means ionization energy values are always positive. In general, larger...

atomic radii and effective nuclear charge

atomic-radii-and-effective-nuclear-charge

Periodic Trends in Atomic Size

Periodic trends in atomic size help explain why atoms get larger or smaller across the periodic table. Elements in the same group show similar chemical behavior because they have the same number and arrangement of valence electrons. Across a period, each new element adds one proton to the nucleus and one electron to the valence shell. Down a group, the number of valence electrons stays the same, but the principal quantum number increases by one. Atomic radius is not easy to define with perfect...

ionic radii

How Ionic Charge Changes Ion Size

Ionic radius describes the size of an ion. It changes when an atom gains or loses electrons. Cations are positive ions with fewer electrons than the parent atom, and they are smaller than the atoms they come from. Aluminum shows this pattern clearly. A neutral aluminum atom has a covalent radius of 118 pm, while Al3+ has an ionic radius of 68 pm. When electrons are removed from the outer valence shell, the remaining core electrons feel a stronger effective nuclear charge, or Zeff. That pull...

electron affinity

Electron affinity is the energy change that happens when a gaseous atom gains an electron and becomes a negative ion, or anion. For many elements, this process releases energy, so the electron affinity value is negative. For some elements, energy must be added instead, so the value is positive. Electron affinity also applies when more than one electron is added. The second electron affinity is the energy change for adding an electron to an anion to make a 2− ion. Later electron affinities...

alkali metals

Alkali Metals: Reactivity Trends

Alkali metals are Group 1 elements with one valence electron. They are soft, shiny metallic solids that are malleable, ductile, and good conductors of heat and electricity. Their melting points are unusually low for metals and drop as you move down the group. Density generally increases down the group, except for potassium. The trend in atomic size helps explain their behavior. Moving from lithium to cesium, each element has a higher principal quantum number, so the outer electron is farther...

halogens

Halogens: Trends and Reactions

Halogens are Group 17 nonmetals that show clear trends in structure and reactivity. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is highly unstable and radioactive, so most of its properties are still unknown because it has a very short half-life. Tennessine is a synthetic element that is also predicted to belong to this group. These elements do not usually exist as single atoms. Instead, they form diatomic molecules, which means...

noble gases

Noble Gases: Sources, Uses, and Reactions

Noble gases are the group 18 elements helium, neon, argon, krypton, xenon, and radon. They were called “noble” because they were once thought to be nonreactive. That idea changed in 1962, when Dr. Neil Bartlett at the University of British Columbia showed that this assumption was not fully correct. These gases occur in very small amounts in the atmosphere. Some natural gas contains 1–2% helium by mass. Helium is separated from natural gas by removing the condensable components, which leaves...

key terms and concepts

Learn how electron affinity changes across the periodic table, why some groups are exceptions, and why chlorine has a more negative value than fluorine.

Electron Affinity Trends on the Periodic Table | 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.

Physical Science

PS.PSc.1.6

Pennsylvania State Academic Standards

Chemical Reactions

3.2.9-12.C

Structure and Properties of Matter

3.2.9-12.A

Louisiana Student Standards for Science

High School

Matter And Its Interactions

HS-PS1-1

HS-PS1-2

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Periodic trends of the elements

Structure And Properties Of Matter

Periodic Table

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.12

Virginia  Standards of Learning

HIgh School

CH.2

CH.2.c

PS.2

PS.2.b

PS.4

PS.4.a

PS.4.b

Arizona Science Standards

HS.P1

HS.P1U1.1

HS+C.P1

HS+C.P1U1.1

Texas Essential Knowledge and Skills

CHEM.5

CHEM.5.A

CHEM.5.C

CHEM.7

CHEM.7.A

Alabama Course of Study Science

9-12.C.1.1

9-12.C.1.1.e

motion-and-stability-forces-and-interactions

Motion and Stability: Forces and Interactions

9-12.C.2.2.f

9-12.PS.3.4.b

Next Generation Science Standards

Chemistry and Physics

IPC.7

IPC.7.B

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Structure and Properties of Matter

HS-PS1-1.

HS. Chemical Reactions

HS-PS1-2.

Georgia Standards of Excellence

SPS1.

Periodic Table Trends

SC1.

periodic-table-trends-atomic-radii-ionization-and-electronegativity

Periodic Table Trends: Atomic Radii, Ionization, and Electronegativity

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Molar Mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

PS.Chm.2.1

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

Analyze the structure of atoms and isotopes.

Electron Affinity Trends on the Periodic Table

Description

Transcript

Tags

More videos by Standards