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

原子轨域具有不同的能量，透过库伦交互作用，屏蔽效应，和轨域穿透来合理化。库伦定律指出两个带电粒 子之间的吸引力或排斥力 与它们之间的距离成平方反比关系。原子轨域尺寸随着壳层数增加，且电子被较低壳层轨 域占据的空间排斥。因此，库伦定律指出随着壳层数 增加，电子对原子核 的吸引力降低，这对应到 更高的轨域能量。除此之外，离原子核大约相等距 离的电子有屏蔽效应 会进一步减少对原子核的吸引力。屏蔽越大，感觉到的对原子核的吸引力越小。这是电子壳层里轨域能量 有所不同的一个原因。例如，3s和3p电子显著的 屏蔽3d电子。电子受到的有效核电荷 透过减去屏蔽常数S来计算，S取决于屏蔽电子的数量 和他们占有的从原子序开始算的副壳层，例如，原子序是三的锂的两个 1s电子，屏蔽了它的2s电子。那个电子的屏蔽常数 由半经验法则决定为1.7。因此，2s电子受到的有效核电荷 是1.3。轨域的形状也是由能量决定。如果在外轨域的电子 可以移动到内电子占有的区域，变得太靠近原子核的话，他们 在那边会被屏蔽的少得多。因此，外轨域的能量较低。这可以透过径向分布函 数来可视化，这个函数描述了 在离原子核给定距离 处找到电子的概率。1s, 2s和2p副壳层的径向分布函数图 揭示，2s电子 在原子核附近的概率适中，而2p电子大多停留在 1s区域的外部或内部。2s轨域，因此被说 是拥有更大的穿透能力。在第三壳层，3s电子 穿透最多，而3d电子穿透最少。通常，原子轨域能量随着壳层数增加 而在副壳层等级上，是从s到f。然而，穿透效应 在第四和第五壳层变得很显著 使得4s和5s轨域通常 有分别相对于3d和4d 轨域低的能量。

原子轨道的能量

在一个原子中，带负电的电子被吸引到带正电的原子核上。在多电子原子中，还观察到电子-电子排斥。吸引力和排斥力取决于粒子之间的距离，以及各个粒子上电荷的符号和大小。当粒子上的电荷相反时，它们会相互吸引。如果两个粒子具有相同的电荷，则它们会互相排斥。
 
 随着电荷量的增加，力的量也增加。然而，当电荷分离更多时，力减小。因此，电子与其核之间的吸引力与它们之间的距离成正比。如果电子更靠近原子核，则它与原子核的结合会更紧密；因此，不同壳（不同距离）中的电子具有不同的能量。
 
 对于具有多个能级的原子，由于电子电子排斥，内部电子部分地屏蔽了外部电子免受原子核的吸引。核心电子屏蔽外壳中的电子，而同一价壳中的电子不会有效地阻碍彼此经历的核吸引。这可以用有效核电荷 Z eff 的概念来解释。考虑到任何电子-电子排斥，这是原子核对特定电子施加的拉力。对于氢，只有一个电子，因此核电荷（ Z ）和有效核电荷（ Z eff ）相等。对于所有其它原子，内部电子部分屏蔽了外部电子免受原子核的吸引，因此：
 
 <img alt =“ Eq1” src =“ https://www.jove.com/files/core/CDNSource/lessons/985/985_Equations-01.png” style =“height: 40px ;“ /> 
 
 轨道穿透描述了电子更靠近原子核的能力。 s 轨道中的电子可以更靠近原子核，并且具有更高的穿透能力。球形 s 轨道的概率密度在原子核处不为零。 ＆nbsp;不同的子壳具有不同的空间方向。由于哑铃形的轨道， p -电子的渗透要少得多。它的波函数有一个穿过原子核的节点，在那里发现电子的概率为零。因此，与 p 电子相比， s 轨道电子与原子核的结合更紧密，能量更低。与 p 轨道电子相比， d 电子具有更低的穿透力和更高的能量。 
 对于各种壳和子壳，电子的穿透能力趋势可以描述如下
 
 <img alt =“ Eq2” src =“ https://www.jove.com/files/core/CDNSource/lessons/985/985_Equations-02.png” style =“height: 40px ;“ /> 
 
 屏蔽和穿透的影响很大，并且4 s 电子的能量可能低于3 d 电子。
 
 本文改编自<a href="https://openstax.org/books/chemistry-2e/pages/6-4-electronic-structure-of-atoms-electron-configurations"> Openstax，化学2e，第6.4节：原子的电子结构（电子结构）。</a>

在原子中，带负电的电子受到带正电原子核的吸引。在多电子原子中，电子与电子之间的排斥作用是……

Education

教育

JoVE Core

Chemistry

化学

Electronic Structure of Atoms

原子的电子结构

KEY TERMS AND CONCEPTS

关键术语与概念

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

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interference and diffraction

Wave Patterns from Light and Slits

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photoelectric effect

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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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the pauli exclusion principle

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

JoVE Core 化学通过简单明了且通俗易懂的动画视频课程，将普通化学概念带入到现实生活当中。此外，在科学家行动视频中，我们演示了在实验室中进行的经典和原始研究实验。

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Matter and its Interactions

PS.Chm.1.3

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Atomic structure

Tennessee Academic Standards

Matter and Its Interactions

CHEM1.PS1.12

Virginia  Standards of Learning

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

HS-PS1-1

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

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

C-PS1-4

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

Georgia Standards of Excellence

SC1.

electron-configuration-and-chemical-properties

Electron Configuration and Chemical Properties

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Ions and Ionic Charges

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

IPC.7.A

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 ...

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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Alkali Metals

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Halogens

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Noble Gases


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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

Phase Transitions: Vaporization and Condensation

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Phase Transitions: Melting and Freezing

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phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

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Melting Points

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Boiling Points

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IPC.7.C

Emission Spectra

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Metal Flame Emission

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Atomic Orbitals

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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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