Name: shielding and orbital penetration
Uploaded: 2020-09-03T13:38:28.000Z
Duration: 3 min 21 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Chemistry and Physics

IPC.7

IPC.7.E

The Energies of Atomic Orbitals

Atomorbitale haben unterschiedliche Energien, wie es durch die Coulomb-Wechselwirkungen erklärt wurde, die abschirmende Wirkung und die orbitale Penetration. Das Coulomb Gesetz besagt, dass die anziehende oder abstoßende Kraft zwischen zwei geladenen Teilchen eine inversquadratische Beziehung, mit dem Abstand dazwischen, hat. Die Größe der Atomorbitale nimmt mit der Schalenzahl zu, und Elektronen werden aus dem besetzten Raum durch untere Schalenorbitale abgestoßen.Das Coulomb Gesetz besagt also, dass wenn die Schalenzahl zunimmt, erfahren die Elektronen weniger Anziehungskraft zum Kern, welches höheren Umlaufbahnenergien entspricht. Darüber hinaus haben Elektronen, die sich in etwa gleichem Abstand vom oder näher am Kern befinden, eine Abschirmung, die die Anziehungskraft des Kerns weiter verringert. Je größer die Abschirmung, wird desto weniger Anziehungskraft des Kerns empfunden.Dies ist ein Grund für die Unterschiede bei orbitalen Energien innerhalb von Elektronenhüllen. Zum Beispiel schirmen 3s-und 3p-Elektronen 3d-Elektronen signifikant ab. Die effektive Kernladung, die ein Elektron spürt, wird durch Subtraktion der Abschirmungskonstante S berechnet, die von der Anzahl der Abschirmelektronen abhängt, und die Unterschalen, die sie besetzen, hängt von der Kernladung ab.Zum Beispiel die beiden 1s-Elektronen in Lithium, das eine Kernladungszahl von drei hat, rastert sein 2s-Elektron. Die Abschirmkonstante für dieses Elektron wird aus semi-empirischen Regeln mit 1, 7 bestimmt. Daher beträgt die effektive Kernladung des 2s-Elektrons 1, 3.Auch die Form der Orbitale diktiert ihre Energie. Wenn die Elektronen in einem äußeren Orbital weit in Bereiche vordringen, die von inneren Elektronen besetzt sind, um dem Kern nahe zu sein, werden sie dort viel weniger abgeschirmt sein. Daher ist die Energie dieses äußeren Orbitals niedriger.Dies kann mit einer radialen Verteilungsfunktionen visualisiert werden, die die Wahrscheinlichkeit beschreibt, ein Elektron in einer gegebenen Entfernung vom Kern zu finden. Diagramme der radialen Verteilungsfunktionen für die 1s, 2s und 2p Unterhüllen zeigen, dass 2s-Elektronen eine bescheidene Wahrscheinlichkeit haben, in der Nähe des Kerns zu sein, während 2p-Elektronen meist außerhalb oder am äußeren Rand der 1s Region bleiben. Es wird daher vermutet, dass das 2s-Orbital ein größeres Durchdringungsvermögen hat.In der dritten Schale durchdringen die 3s-Elektronen am meisten und die 3d-Elektronen am wenigsten. Im Allgemeinen steigt die atomare Orbitalenergie mit der Schalenzahl und auf der Unterschalen-ebene von s bis f. Der Penetrationseffekt wird jedoch so signifikant in der vierten und fünften Schale, dass die 4er-und 5er-Orbitale häufig niedrigere relative Energien haben als die 3d-und 4d-Orbitale.

energie der atomorbitale

In einem Atom werden die negativ geladenen Elektronen vom positiv geladenen Kern angezogen. In einem Atom mit mehreren Elektronen werden auch Elektron-Elektron-Abstoßungen beobachtet. Die anziehenden und abstoßenden Kräfte hängen vom Abstand zwischen den Teilchen sowie vom Vorzeichen und der Größe der Ladungen auf den einzelnen Teilchen ab. Wenn die Ladungen der Teilchen entgegengesetzt sind, ziehen sie sich gegenseitig an. Besitzen beide Teilchen Ladung gleichen Vorzeichens, stoßen sie sich gegenseitig ab. Mit zunehmender Größe der Ladungen nimmt auch die Größe der Kraft zu. Mit größerer Distanz nimmt die entsprechende Kraft jedoch ab. Somit ist die Anziehungskraft zwischen einem Elektron und seinem Kern direkt proportional zum Abstand zwischen ihnen. Befindet sich das Elektron näher am Kern, ist es fester an ihn gebunden; Daher haben die Elektronen in den verschiedenen Orbitalen (und somit unterschiedlichen Abständen) unterschiedliche Energien. Bei Atomen mit mehreren Energieniveaus schirmen die inneren Elektronen die äußeren Elektronen aufgrund von Elektron-Elektron-Abstoßungen teilweise vor der Anziehungskraft des Kerns ab. Kernelektronen schirmen die Elektronen in den äußeren Schalen ab, während Elektronen in derselben Valenzschale die gegenseitige Kernanziehung nicht maßgeblich beeinflussen. Dies kann mit dem Konzept der effektiven Kernladung Zeff erklärt werden. Dies ist die Anziehungskraft, die der Kern auf ein bestimmtes Elektron ausübt, wobei etwaige Elektron-Elektron-Abstoßungen berücksichtigt werden. Für Wasserstoff gibt es nur ein Elektron, daher sind die Kernladung (Z) und die effektive Kernladung (Zeff) gleich. Bei allen anderen Atomen schirmen die inneren Elektronen die äußeren Elektronen teilweise vor der Anziehungskraft des Kerns ab und somit: <img alt="Eq1" src="https://www.jove.com/files/core/CDNSource/lessons/985/985_Equations-01.png" style="height: 40px;"> Die Orbitalpenetration beschreibt die Fähigkeit eines Elektrons, sich dem Kern anzunähern. Die Elektronen im s-Orbital können näher an den Kern herankommen und haben damit eine tiefer reichende Anziehungskraft. Die Wahrscheinlichkeitsdichte für ein sphärisches s-Orbital ist am Kern ungleich Null. Unterschiedliche Unterschalen haben unterschiedliche räumliche Ausrichtungen. Aufgrund des hantelförmigen Orbitals der p-Elektronen dringen diese deutlich weniger tief ein. Ihre Wellenfunktion hat einen Knoten, der durch den Kern verläuft, dort ist die Wahrscheinlichkeit, das Elektron zu finden gleich Null. Daher ist ein s-Orbitalelektron fester an den Kern gebunden und hat eine geringere Energie als das p-Elektron. Ein d-Elektron durchdringt den Kern noch weniger und hat eine höhere Energie als ein p-Orbitalelektron. Für verschiedene Schalen und Unterschalen lässt sich der Verlauf der Anziehungskraft eines Elektrons wie folgt darstellen <img alt="Eq2" src="https://www.jove.com/files/core/CDNSource/lessons/985/985_Equations-02.png" style="height: 40px;"> Der Effekt der Abschirmung und die der Anziehung ist groß und ein 4s-Elektron kann eine niedrigere Energie haben als ein 3d-Elektron. Dieser Text wurde adaptiert von <a href="https://openstax.org/books/chemistry-2e/pages/6-4-electronic-structure-of-atoms-electron-configurations">Openstax, Chemistry 2e, Section 6.4: Electronic Structure of Atoms (Electron Configurations).</a>

Energie der Atomorbitale

In einem Atom werden die negativ geladenen Elektronen vom positiv geladenen Kern angezogen. In einem Multielektronenatom sind Elektron-Elektron-Abstoßungen ...

Education

Lehre

JoVE Core

Chemistry

Chemie

Eins

Electronic Structure of Atoms

Elektronische Struktur von Atomen

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

shielding and orbital penetration

Shielding and orbital penetration help explain why electrons in an atom have different energies. Electrons are attracted to the positive nucleus, but they also repel one another in atoms with more than one electron. The strength of these forces depends on the charge and the distance between the particles. Opposite charges attract, like charges repel, and the force gets weaker as the particles move farther apart.

An electron that stays closer to the nucleus is held more tightly. That means electrons in different shells can have different energies because they sit at different distances from the nucleus. In atoms with several energy levels, inner electrons partly block the nucleus from outer electrons. This blocking is called shielding, and it happens because of electron-electron repulsions.

The pull felt by one electron after shielding is the effective nuclear charge, or Zeff. It describes the attraction from the nucleus after repulsions are taken into account. For hydrogen, which has only one electron, Z and Zeff are the same. In atoms with more than one electron, core electrons shield outer electrons, while electrons in the same valence shell do not block the nuclear pull very well.

Orbital penetration describes how close an electron can get to the nucleus. s orbitals penetrate best because their spherical probability density is non-zero at the nucleus. p orbitals penetrate less because their dumbbell shape has a node through the nucleus, where the chance of finding an electron is zero. d orbitals penetrate even less than p orbitals.

Because of shielding and penetration, s electrons are usually bound more tightly and have lower energy than p electrons. d electrons have higher energy than p electrons. These effects can be strong enough that a 4s electron may have lower energy than a 3d electron.

Shielding and Orbital Penetration

the wave nature of light

Measuring Light with Wavelength and Frequency

Light can be described as an electromagnetic wave, and its behavior helps explain many patterns seen in science. For centuries, scientists have tried to understand light. Newton used lenses and prisms to show that white light is made of the colors of the rainbow mixed together. He explained light as tiny particles moving at high speed. Other scientists, including Christiaan Huygens, showed that reflection and refraction could also be explained by treating light as a wave. At the time, people...

the electromagnetic spectrum

Electromagnetic Waves: Uses Across the Spectrum

The electromagnetic spectrum includes all electromagnetic radiation arranged by frequency and wavelength. Visible light is only a small part of it, and each color of visible light has its own frequency and wavelength. Different parts of the spectrum also use different units. Radio waves are usually measured in MHz, while the visible range is often measured in nm or angstroms. The spectrum is organized from radio waves to gamma rays as frequency increases and wavelength decreases. Radio waves...

interference and diffraction

Wave Patterns from Light and Slits

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Why Light Ejects Electrons from Metals

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the bohr model

Bohr’s Quantized Atomic Orbits

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emission spectra

Line Spectra from Heated Gases

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the de broglie wavelength

Electron Waves and Standing Orbits

Electron waves and standing orbits explain how tiny particles can behave like waves. Large objects in the macroscopic world, like a billiard ball on a table, follow classical physics. A ball keeps moving in a straight line unless it hits another ball or a force such as friction acts on it. It also has a well-defined position, velocity, and momentum, where momentum is mass times velocity. Waves behave differently from macroscopic particles. When waves interact, they can form interference...

the uncertainty principle

Electron Position and Momentum Limits

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the quantum-mechanical model of an atom

Electron Orbitals in Quantum Mechanics

Quantum mechanics explains how electrons behave in atoms using waves and probability. Erwin Schrödinger built on de Broglie’s idea that an electron in hydrogen could act like a circular standing wave instead of moving in fixed circular paths. He then derived the Schrödinger equation, which became a major step in modern atomic theory. When Schrödinger applied his equation to hydrogen-like atoms, it matched Bohr’s energy expression and the Rydberg formula for hydrogen spectra. He described...

quantum numbers

Electron Orbitals and Spin

Electron orbitals are described by quantum numbers that show where an electron is most likely to be found around the nucleus. These numbers come from the quantum mechanical model, which is based on solutions of the Schrödinger equation. They also help explain why electron energy comes in set values instead of changing smoothly. The principal quantum number, n, labels the energy level. It can be 1, 2, 3, and so on, and higher n values usually mean higher electron energy. This number also tells...

atomic orbitals

Electron Regions in Atomic Orbitals

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Electron Spin and Orbital Pairing

Electron spin and orbital pairing explain why only two electrons can fit in one atomic orbital. Electron configuration describes how electrons are arranged in an atom’s orbitals. It is written with three parts: the principal quantum number, n, the orbital type, or subshell, and a superscript that shows how many electrons are in that subshell. For example, 2p4 means four electrons in a p subshell with n = 2, and 3d8 means eight electrons in a d subshell with n = 3. The three quantum numbers...

the energies of atomic orbitals

Shielding and orbital penetration help explain why electrons in an atom have different energies. Electrons are attracted to the positive nucleus, but they also repel one another in atoms with more than one electron. The strength of these forces depends on the charge and the distance between the particles. Opposite charges attract, like charges repel, and the force gets weaker as the particles move farther apart. An electron that stays closer to the nucleus is held more tightly. That means...

the aufbau principle and hund's rule

Electron Filling Order in Atomic Orbitals

Electron filling order in atomic orbitals follows the aufbau principle and Hund's rule. To write an electron configuration, we build atoms in order of atomic number. Starting with hydrogen and moving across the periods of the periodic table, one proton is added to the nucleus and one electron is placed into the correct subshell. This process describes the ground-state electron configurations of the elements. The aufbau principle comes from the German word aufbau, which means "to build up." It...

electron configuration of multielectron atoms

electron-configuration-of-multielectron-atoms

Valence Electrons and Noble Gas Shorthand

Valence electrons and noble gas shorthand help show how electrons are arranged in multielectron atoms. Sodium, the alkali metal with atomic number 11, has one more electron than neon. That extra electron goes into the lowest-energy subshell available, the 3s orbital, so sodium has the configuration 1s2 2s2 2p6 3s1. Electrons in the outermost shell, where n is highest, are called valence electrons. Electrons in the inner shells are called core electrons. Because core electrons often match a...

key terms and concepts

Learn how shielding, effective nuclear charge, and orbital penetration affect electron energy levels, and why s, p, and d orbitals differ in energy.

Shielding and Orbital Penetration | JoVE K12

chemistry

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NC K-12 Science Standard Course of Study

9-12

Matter and its Interactions

PS.Chm.1.3

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Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Atomic structure

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.12

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HIgh School

CH.2

CH.2.e

Physical Science

PS.2

PS.2.a

CHEM.6

CHEM.6.B

Alabama Course of Study Science

9-12.C.1.1.c

Next Generation Science Standards

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Florida Department of Education

SC.912.P.8

SC.912.P.8.5

SC.912.P.10

SC.912.P.10.9

IPC.7.D

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South Carolina College and Career Ready Science Standards

C-PS1-4

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New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

Georgia Standards of Excellence

SC1.

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Electron Configuration and Chemical Properties

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The Periodic Table

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Molar Mass

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Periodic Classification of the Elements

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Types of Chemical Bonds

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Ionic Bonding and Electron Transfer

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Trends in Lattice Energy: Ion Size and Charge

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Bond Polarity

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Lewis Structures of Molecular Compounds and Polyatomic Ions

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	Determine the ...

Bond Energies and Bond Lengths

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Bonding in Metals

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Model basic atomic structure and relate an element's atomic structure to its bonding, reactivity, and placement on the Periodic Table.

IPC.7.A

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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 ...

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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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This process can be either ...

Alkali Metals

Group 1 elements are soft and shiny metallic solids. They are malleable, ductile, and good conductors of heat and electricity. The melting points of the ...

Halogens

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Noble Gases


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Use patterns within the Periodic Table to predict the relative physical and chemical properties of elements.

IPC.7.B

Classifying Matter by State

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Classifying Matter by Composition

Matter: Pure Substances and Mixtures
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Phase Transitions

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Phase Transitions: Vaporization and Condensation

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Melting Points

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Boiling Points

Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA

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Explain how physical and chemical properties of substances are related to their usage in everyday life such as in sunscreen, cookware, industrial applications, and fuels.

IPC.7.C

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 ...

Metal Flame Emission

Metal Flame Emission
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Explain how electrons can transition from a high energy level to a low energy state, emitting photons at different frequencies for different energy transitions.

Science concepts. The student knows that relationships exist between the structure and properties of matter. The student is expected to:

Shielding and Orbital Penetration

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