Name: hydrogen emission lines
Uploaded: 2020-03-26T07:22:25.000Z
Duration: 3 min 53 s
Channel: JoVE

K12 Standards

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Chemistry and Physics

IPC.7

IPC.7.E

Balmer Series

原子和分子在吸收和释放能量时会表现出非常有趣的行为。原子中的电子通常处于最低能量状态，称为基态，标记为 n 等于 1。然而，当原子吸收能量时，电子会被激发并跃迁到更高的能级。当电子弛豫回到较低能量状态或基态时，多余的能量会以发射光的形式释放出来。
您可能对这些能态较为熟悉，它们在玻尔模型中有所体现，该模型将原子描述为具有围绕原子核运行的电子，这些电子位于壳层或轨道上。这些壳层与能级相同，并用 n 标记。所发射光的波长取决于高能级与低能级之间的差值。高能光的发射源于电子从较高能级弛豫，而低能光的发射则源于电子从较低能级弛豫。
发射光谱用于测量在一定波长范围内发射的辐射。对于纯元素物质，其发射行为表现为特定波长的谱线，而非连续的宽谱带。由于不同原子具有不同的能级，这些谱线随元素而异，取决于电子受激发时在不同能级之间跃迁的方式。例如，氢原子有六个命名的谱线系，其中之一是巴尔末系。
当电子从高于 n = 3 的能级跃迁回 n = 2 能级时，会产生谱线的巴尔末系。巴尔末系的可见光光谱表现为位于 410 nm、434 nm、486 nm 和 656 nm 处的谱线。Hα 谱线是位于 656 nm 的红光谱线，由 n = 3 到 n = 2 的能级跃迁产生。青色、蓝色和紫色谱线分别对应于从 n = 4、5 和 6 能级向 n = 2 能级的跃迁。此外，还可测量到位于可见光范围之外的其他谱线。
约翰·巴尔默使用巴尔默公式对可见光谱线进行了量化。其中，λ 是观测到的波长，c 是一个常数，n 是较低的能级（为2），m 是较高的能级。将巴尔默公式与玻尔模型结合，可得到里德伯公式，该公式可用于描述多种不同元素的光谱线。在此公式中，λ 是记录的波长，RH 是里德伯常数。标记为 n 初的初始能级代表电子被激发至的较高能级，而 n 末是电子弛豫返回的较低能级。对于巴尔末系，n最终 = 2.
在本实验中，您将测量并观察氢、氦和氖的发射光谱，并利用里德伯方程确定谱线的位置。

巴尔末系

玻尔模型
尼尔斯·玻尔于1913年提出了氢原子模型，指出电子在原子核周围特定的固定轨道上运动，并对应着分立的能量状态。重要的是，当电子处于定态时，原子不会释放能量。电子只有在改变能量状态时才能发射能量。要改变能量状态，电子必须通过吸收或发射能量从一个轨道跃迁到另一个轨道。这种跃迁只有在吸收或发射的能量等于两个状态之间的能量差时才能发生。电子不能存在于轨道之间。
量子数 n 用于标记不同的能级。能量最低的状态称为基态，对应 n 等于 1。激发态则依次标记为 n 等于 2、3、4，依此类推。当处于基态的电子吸收一个光子，且该光子的能量恰好等于基态与第二能级之间的能量差时，电子将被激发，并从基态跃迁至 n = 2 的激发态。如果光子的能量等于基态与第三能级之间的能量差，电子则会跃迁至 n = 3 的能级。
根据玻尔模型，第 n级能级中电子的势能可通过以下公式计算：
<img src="/CDNSource/lm/labs/54/54_Concepts_1.jpg" alt="玻尔模型能级公式，En=-Rhc/n²，与电子跃迁相关，方程。" data-altupdatedat="1754904545000" data-alt="玻尔模型能量方程 \(E_n=-\frac{Rhc}{n^2}\)，量子力学概念。" />
其中，En 为势能，R 为里德伯常数（1.0974 × 107 m-1），h 为普朗克常数（6.62607004 × 10-34 m2·kg/s），c 为光速（约 3 × 108 m/s）。电子也可以自发地回到基态或任何其他较低的激发态。当发生这种情况时，多余的能量以发射光子的形式释放出来。光子的能量等于较高能级与较低能级之间的能量差。该能量对应于特定波长的光。由于每种类型的原子具有不同的能级，因此每种原子在跃迁时所发射的光也各不相同。对于含有多种分子的样品，所发射的光包含一系列波长，称为连续光谱。而对于仅含单一元素原子的样品，所发射的光仅包含某些特定波长，经棱镜分光后可观察到离散的谱线。
<h4>氢原子</h4>
具体以氢原子为例，其电子的激发需要吸收足够的能量，以断裂双原子分子 H2 中的化学键。由于断裂分子所需的能量超过实际需要，氢原子中的电子会吸收多余的能量，从而被激发至更高的能级。当电子自发地回到较低能级时，便会释放出光，其能量对应于激发态与较低能级之间的能量差。
在讨论能量发射时，较高能级被视为初始能级，即 ni，而较低能级则被视为最终能级，即 nf。所发射光的波长最终取决于这两个能级之间的能量差。
在纯氢气样品中，发射光谱呈现为一系列特定于氢元素的、具有离散波长的清晰谱线。其中一些谱线位于电磁波谱的可见光范围内，而另一些则位于紫外或红外范围内。
<h4>巴尔末系</h4>
氢原子光谱中的可见光谱线系列被称为巴尔末系。该系列的光谱发射线产生于电子从高能级跃迁至 n=2 的低能级时。约翰·巴尔末观测到这些谱线的波长分别为 410.2 nm、434.1 nm、486.1 nm 和 656.3 nm，分别对应于电子从 n=6、n=5、n=4 和 n=3 能级向 n=2 能级的跃迁。
巴尔默能够使用巴尔默公式来关联这些发射光的波长。
<img src="/CDNSource/lm/labs/54/54_Concepts_2.jpg" alt="波长计算公式 &#955;=C(m&#178;/(m&#178;-n&#178;))，光谱分析方程。" data-altupdatedat="1754904545000" data-alt="波长公式 &#955;=C(m&#178;/(m&#178;&#8722;n&#178;))；物理方程；用于波动分析的示意图。" />
此处，λ 为观测到的波长，C 为常数（364.50682 nm），n 为较低能级，其值为 2，m 为较高能级，其值大于 3。随后，约翰内斯·里德伯（Johannes Rydberg）对此进行了改进，其中 R 为里德伯常数。
<img src="/CDNSource/lm/labs/54/54_Concepts_3.jpg" alt="里德伯公式方程；用于计算原子光谱学中的谱线。" data-altupdatedat="1754904545000" data-alt="谱线的里德伯公式、方程、物理学、光谱计算。" />
请记住，该方程描述的是发射光，因此较高能级被视为初始能级，即 ni，而较低能级被视为最终能级，即 nf。对于巴尔末系，nf 等于 2。该方程与玻尔模型结合，用于计算电子从初始能级跃迁到最终能级所需的能量变化 ΔE。
<img src="/CDNSource/lm/labs/54/54_Concepts_4.jpg" alt="能级跃迁方程 \(\Delta E = Rhc(\frac{1}{n_f^2} - \frac{1}{n_i^2})\)；物理学公式。" data-altupdatedat="1754904545000" data-alt="能量变化公式，&#916;E=Rhc(1/nf&#178;-1/ni&#178;)，光谱跃迁方程，量子物理。" />
后来，人们又发现了氢原子的其他光谱系。例如，莱曼系包含能量位于紫外区的发射谱线。
<h4>参考文献</h4>
<ol>
	<li style="font-size:17px">Kotz, J.C., Treichel Jr, P.M., Townsend, J.R. (2012). 化学与化学反应性。加利福尼亚州贝尔蒙特：Brooks/Cole, Cengage Learning。</li>
	<li style="font-size:17px">Silderberg, M.S. (2009). 化学：物质的分子本质与变化。马萨诸塞州波士顿：McGraw Hill。</li>
</ol>

玻尔模型  
尼尔斯·Bohr 于1913年提出了氢原子模型，该模型指出，离散的能量状态与固定的电子轨道相对应……

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Balmer 系列

hydrogen emission lines

Hydrogen emission lines show how electrons move between fixed energy levels in the Bohr model. Niels Bohr proposed this model for the hydrogen atom in 1913. In this model, an electron can only occupy certain orbits, and it cannot exist between them.

These energy states are labeled with the quantum number n. The ground state is n = 1. Higher values, such as n = 2, 3, 4, and so on, are excited states. An electron changes state only by absorbing or emitting energy equal to the difference between two levels. A photon with the right energy can move an electron from one orbit to another.

Bohr’s model also links each energy level to a specific amount of potential energy. That value can be calculated with an equation that uses the Rydberg constant, Planck’s constant, and the speed of light. When an electron returns to the ground state or another lower excited state, it releases the extra energy as a photon. The photon energy matches the gap between the two states, so it also determines the wavelength of the emitted light.

Because each atom has its own energy levels, each element gives off its own pattern of light. A mixed sample can produce a continuous spectrum with many wavelengths. A pure sample of one element produces only certain wavelengths. When that light passes through a prism, it appears as separate lines instead of one smooth band.

Hydrogen shows this pattern clearly. Exciting hydrogen atoms requires enough energy to split the H2 molecule, and the extra energy excites the hydrogen electrons to higher levels. When those electrons drop back down, they emit light at wavelengths set by the energy difference between the initial level, n i, and the final level, n f. In pure hydrogen gas, this emission spectrum contains distinct visible, ultraviolet, and infrared lines that are unique to hydrogen.

The visible lines in hydrogen are called the Balmer series. They occur when an electron falls to n = 2 from a higher level. Johann Balmer observed lines at 410.2 nm, 434.1 nm, 486.1 nm, and 656.3 nm, which match transitions from n = 6, 5, 4, and 3 to n = 2. He described these wavelengths with the Balmer formula, where λ is the observed wavelength, C is a constant of 364.50682 nm, n is the lower level, and m is the higher level.

Later, Johannes Rydberg refined this idea using the Rydberg constant. For the Balmer series, the final level n f equals 2. The same relationship, combined with the Bohr model, can be used to calculate the energy change, ΔE, for electron transitions. Other hydrogen spectral series were later identified as well, including the Lyman series, which lies in the ultraviolet region.

Hydrogen Emission Lines

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Steam Distillation and Low-Boiling Separation

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chemistry

Comprehensive, curriculum-focused videos for both instructors and students in introductory chemistry lab courses.

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Explore how hydrogen electrons jump between energy levels and produce discrete emission lines, including the visible Balmer series and other hydrogen spectra.

Hydrogen Emission Lines | JoVE K12

Louisiana Student Standards for Science

motion-and-stability-forces-and-interactions

Motion And Stability: Forces And Interactions

HS-PS2-6

Tennessee Academic Standards

waves-and-their-applications-in-technologies-for-information-transfer

Waves and Their Applications in Technologies for Information Transfer

CHEM1.PS4.1

Next Generation Science Standards

Earth and Space Science

Earth’s Place in the Universe

HS-ESS1-2

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

South Carolina College and Career Ready Science Standards

Matter and Its Interactions

C-PS1-4

Georgia Standards of Excellence

9-12

SC1.

Light Emission and Electron Movement

通过这段 1 分钟的教师指南，准备教授 巴尔末系。涵盖 JoVE Lab Manual 上 Chemistry 实验的关键准备步骤。

Chemistry 中的 巴尔末系 教师准备 - 2.0K+ 观看次数 | JoVE Lab Manual

在这段 4 分钟的学生实验流程视频中，逐步学习 巴尔末系 的操作步骤。属于 JoVE Lab Manual 上的 Chemistry 系列。

Chemistry 中的 巴尔末系 学生实验流程 - 5.1K+ 观看次数 | JoVE Lab Manual

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 ...

Ions and Ionic Charges

In ordinary chemical reactions, the nucleus &mdash; which contains the protons and neutrons of each atom and thus identifies the element &mdash; remains ...

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, ...

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 ...

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 ...

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 ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Bonding in Metals

Metallic bonds are formed between two metal atoms. A simplified model to describe metallic bonding has been developed by Paul Dr&#xFC;de called the ...

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

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 ...

Electron Affinity

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 ...

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 ...

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

IPC.7.B

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

Hydrogen Emission Lines

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