Name: electron shells and discovery
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 9 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-1

Electron Behavior

电子是微小的带负电粒子，存在于带正电原子核周围的电子云中。在电子云内，电子位于称为电子层或能级的特定区域。
能级通常使用简化的玻尔模型或行星模型来可视化，其中能级被表示为围绕原子核的环状结构，尽管它们实际上具有复杂的形状。
这些电子层中的电子离原子核越远，能量越高。
第一能级最多可容纳两个电子。第二电子层最多可容纳八个电子。原子中的额外电子将依次填充能量更高的能级。
最外层占据轨道中的电子称为价电子，它们决定了元素的化学性质。
价电子可以在原子之间共享，形成共价键，或者发生转移，形成离子键。&#160;

电子行为

电子是带负电的亚原子粒子，它能够被吸引并围绕着带正电的原子核周围进行轨道运动。它们出现在与能级（称为壳层）相关的空间中，并在每个壳层内进一步组织形成亚壳层和轨道。

电子绕核运动

电子存在于核外的特定位置。电子所在的壳层表示电子的一般能量水平：离核更近的电子能量较低，而离核更远的电子则能量较高。亚壳层更准确地描述了电子的位置和能量水平，而轨道则描述了电子绕核运动可能出现的区域所形成的形状。离核最近的电子具有最少的能量，随着它们与核之间的距离增加，携带的能量也增加。离核越远，电子能够绕行的空间越多，使得外层壳层能够容纳比内层壳层更多的电子。原子的最外层电子存在于价壳层中，并被称为价电子。这些电子可以与其他原子形成离子和共价键。

发现电子

在19世纪90年代末，汤姆孙（J.J. Thomson）进行了一系列使用阴极射线管的实验，这些实验最终导致了电子中第一个亚原子粒子的发现。阴极射线管是一个玻璃管，是由两个电极连接到供电的电源。真空将其内部的大部分空气排除出到管内。当电压施加在电极上时，从带负电的阴极到带正电的阳极方向会有一束粒子产生运动。阳极上有一个小孔会让射线通过。在管的另一端涂有磷，当阴极射线击中它时将会发光。

汤姆孙将阴极射线固定在两块金属板之间，其中一块带正电，另一块带负电，同时并测量射线在板末端的位置。当射线穿过这两块金属板时，它会偏离带负电的金属板，向带正电的板子的方向弯曲。根据同性相斥，异性相吸的法则，可以由此推断出阴极射线中的粒子带有负电荷。

通过进一步的实验来计算阴极粒子的质荷比，结果显示每个带负电粒子的质量约为任何已知原子的1/2000。汤姆孙由此得出结论，任何给定的原子中必须存在许多电子。随后，质子和中子的发现解释了原子的质量的分布情况和整体的电荷属性。

本文改编自 <a href="https://openstax.org/books/chemistry-2e/pages/6-3-development-of-quantum-theory#0">Openstax, Chemistry 2e, Section 6.3: Development of quantum theory</a>.

电子是带负电的亚原子粒子，被带正电的原子核吸引并在其周围轨道运行。它们存在于空间……

Education

教育

JoVE Core

Anatomy and Physiology

解剖学与生理学

Unit 1

第 1 单元

Fundamentals of Chemistry

化学基础

KEY TERMS AND CONCEPTS

关键术语与概念

electron shells and discovery

Electrons are negatively charged subatomic particles that stay near the positively charged nucleus of an atom. They occupy spaces linked to energy levels called shells. They are also arranged into subshells and orbitals within each shell.

An electron’s shell shows its general energy level. Electrons closer to the nucleus have less energy, while electrons farther away have more energy. The outer shells have more space, so they can hold more electrons than the inner shells.

Subshells describe an electron’s location and energy more precisely. Orbitals describe the shape of an area of probability where an electron may move around the nucleus. The outermost electrons are found in the valence shell and are called valence electrons. These electrons can form ionic and covalent bonds with other atoms.

J. J. Thomson discovered the electron in the late 1890s through experiments with cathode ray tubes. A cathode ray tube is a glass tube with two electrodes, a power source, and a vacuum that removes most of the air. When voltage is applied, a beam of particles travels from the negatively charged cathode to the positively charged anode, and a phosphorus coating glows when the beam strikes it.

Thomson also sent the cathode ray between two metal plates, one positive and one negative. The ray bent away from the negatively charged plate and toward the positively charged plate. This showed that the particles carried a negative charge, since like charges repel and opposite charges attract.

Further experiments showed that each particle had a mass about 1/2000 of the mass of any known atom. Thomson concluded that atoms must contain many electrons. Later, the discovery of protons and neutrons helped explain how an atom’s mass is spread out and why its overall charge is neutral.

Electron Shells and Discovery

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factors influencing the rate of chemical reactions

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key terms and concepts

Explore how electrons are arranged in shells, subshells, and orbitals, and how J. J. Thomson discovered the electron using cathode ray tubes.

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

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Physics

Motion and Stability: Forces and Interactions

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HS-PS1-4

Electron Shells and Discovery

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