Name: line spectra from heated gases
Uploaded: 2020-09-03T13:38:27.000Z
Duration: 2 min 39 s
Channel: JoVE

K12 Standards

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

NC K-12 Science Standard Course of Study

9-12

Physical Science

Matter and its Interactions

PS.PSc.1.4

Emission Spectra

当一个原子吸收能量时，电子 就会被激发并移动到更高的能级。当电子向下弛豫到较低的能量状态 或基态时，多余的能量 会以光子的形式释放出来。吸收和发射的光的波长 取决于高低能级之间的 差异。高能量发射的光是 由电子从较高能级弛豫而来，而低能量发射的光是由电子 从较低能级弛豫而来。发射光谱是对在一系列波长范围内发射的 辐射的测量。对于纯元素物质，发射行为 表现为特定波长的线条 而不是宽光谱。这是氢的发射光谱。可见光区域的光谱线的集合 被称为巴尔默（Balmer）系列。它发生在电子从 高于 n=3 的能级跃迁回 n=2 的能级时。可见光的光谱在 410、434、486 和 656 nm 处以谱线的形式 出现，分别对应于从 n 3、4、5 和 6 到 n=2 的能级跃迁。可以在可见光的范围之外 测量其他光谱线，例如在 紫外区域的莱曼（Lyman）系列和在 红外区域的帕申（Paschen）系列。氢的光谱线的波长 可以用一个数学表达式来预测，其中 R-H 为里德伯常数，n1 是较低能级的主量子数，而 n2 是较高能级的 主量子数。对于巴尔默系列，n1=2。由于不同的原子具有不同的能级，光谱发射线因元素而异，因此可以用于识别物质。与发射光谱相反的 是它的吸收光谱。来看一下氢，它的吸收光谱中的谱线 位于发射光谱的相同波长 处，但它们是暗的。这些是当氢原子 暴露在连续的白光光谱中时 被氢原子吸收的光的 波长。

发射光谱

当固体，液体或冷凝气体充分加热时，它们会以光的形式辐射一些多余的能量。以这种方式产生的光子具有一定范围的能量，从而产生连续光谱，其中存在连续的一系列波长。
 
 与连续光谱相反，光也可能以散布在整个光谱区域中的非常窄的线宽的离散光谱或线光谱出现。使用电流激发低分压的气体或对其加热会产生线谱。荧光灯和霓虹灯以这种方式工作。尽管分子的光谱通常要复杂得多，但每个分子和分子都显示出自己的特征线集。
 
 每条发射线由一个单一波长的光组成，这意味着气体发出的光由一组离散的能量组成。例如，当放电通过含有低压氢气的管时，H 2分子被分解成单独的H原子，并观察到蓝粉红色。使光通过棱镜会产生线谱，表明该光由四个可见波长的光子组成。
 
 在19世纪后期，科学家们对原子和分子中离散光谱的起源极为困惑。根据经典电磁理论，仅应观察到连续光谱。在UV和IR区域发现了氢原子的其他离散谱线。约翰尼斯·赖德伯格（Johannes Rydberg）推广了巴尔默的工作，并开发了一个经验公式，该公式可以预测所有氢的发射线，而不仅限于那些可见光范围，其中 n 1 和 n 2 是整数， n 1 ＆lt; n 2 
 
 <img alt =“ Eq1” src =“ https://www.jove.com/files/core/CDNSource/lessons/977/977_Equations-01.png” style =“height: 40px ;“ /> 
 
 即使在19世纪后期，光谱学也是一门非常精确的科学，因此对氢的波长进行了非常高精度的测量，这意味着也可以非常精确地确定Rydberg常数。像里德伯格公式这样的简单公式可以解释如此精确的测量，这在当时似乎是令人吃惊的，但这是尼尔·玻尔（Neils Bohr）在1913年对发射光谱的最终解释，最终说服科学家放弃了经典物理学，并刺激了现代量子技术的发展。机械师。
 
 本文改编自<a href="https://openstax.org/books/chemistry-atoms-first-2e/pages/3-1-electromagnetic-energy"> Openstax，化学2e，第3.1节：电磁能</a>。

当固体、液体或凝聚态气体被充分加热时，会以光的形式辐射出部分多余能量。以此方式产生的光子具有……

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

line spectra from heated gases

Line spectra are produced when heated gases give off light at specific wavelengths. In contrast, hot solids, liquids, or condensed gases radiate excess energy as a continuous spectrum. That spectrum contains an unbroken range of wavelengths.

A gas at low partial pressure can produce a line spectrum when it is excited by an electric current or heated. Fluorescent light bulbs and neon signs work in this way. Each element has its own characteristic set of lines, and molecules can also produce line spectra, although their patterns are usually more complex.

Each emission line is a single wavelength of light. That means the light from a gas is made of discrete energies rather than a smooth spread of values. A good example is hydrogen gas in an electric discharge tube. The H2 molecules break apart into separate H atoms, and the gas gives off a blue-pink color.

When that light is passed through a prism, it separates into a line spectrum. For hydrogen, this shows four visible wavelengths. Scientists also found other hydrogen lines in the ultraviolet and infrared regions. In the late nineteenth century, these discrete spectra were hard to explain because classical electromagnetic theory predicted only continuous spectra.

Johannes Rydberg extended Balmer's work and wrote an empirical formula that predicted all of hydrogen's emission lines, not just the visible ones. The wavelengths of hydrogen were measured with high accuracy, so the Rydberg constant could also be determined very precisely. Later, Niels Bohr explained emission spectra in 1913. His explanation helped push scientists away from classical physics and toward modern quantum mechanics.

Line Spectra from Heated Gases

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

Light can form wave patterns through interference and diffraction. When two electromagnetic waves meet with their peaks and troughs lined up, they combine into a larger wave. This is constructive interference, and the waves are in phase. When a peak of one wave meets a trough of the other, the waves reduce each other. This is destructive interference, and the result has a much lower amplitude. Diffraction is another wave behavior. When light passes through a slit that is about the same size as...

photoelectric effect

Why Light Ejects Electrons from Metals

Light can eject electrons from a metal surface when it has the right frequency. This process is called the photoelectric effect. Each metal has its own threshold frequency, which is the minimum light frequency needed to free electrons. Light below the threshold frequency cannot cause emission, even if it is very bright. When the light frequency is above the threshold, electrons are ejected. In that case, the number of electrons released is directly proportional to the intensity, or brightness,...

the bohr model

Bohr’s Quantized Atomic Orbits

Bohr’s quantized atomic orbits explain why hydrogen atoms can stay stable. Early in the twentieth century, Ernest Rutherford and his colleagues described atoms as tiny dense nuclei with lighter electrons moving around them. This picture was called the planetary model because it compared the atom to a miniature solar system, with electrons orbiting the nucleus like planets around the sun. The simplest atom is hydrogen. It has one proton in the nucleus and one electron moving around it. In the...

emission spectra

Line spectra are produced when heated gases give off light at specific wavelengths. In contrast, hot solids, liquids, or condensed gases radiate excess energy as a continuous spectrum. That spectrum contains an unbroken range of wavelengths. A gas at low partial pressure can produce a line spectrum when it is excited by an electric current or heated. Fluorescent light bulbs and neon signs work in this way. Each element has its own characteristic set of lines, and molecules can also produce...

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

Heisenberg’s uncertainty principle sets a limit on how precisely we can know an electron’s position and momentum at the same time. Momentum is the motion of a particle, and the two measurements affect each other. If the momentum is known more accurately, the position becomes less certain, and the reverse is also true. Heisenberg described this limit with an equation that uses Planck’s constant. The equation shows the smallest possible uncertainty for position and momentum together. It explains...

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

Electron regions in atomic orbitals show where an electron is most likely to be found in an atom. These three-dimensional regions are often drawn as boundary surfaces around the densest part of the cloud. The shape of an orbital depends on the angular momentum quantum number, l. This value can range from 0 to n - 1, where n is the principal quantum number. For n = 1, only l = 0 is allowed. For n = 2, both l = 0 and l = 1 are allowed. Orbitals with the same value of l form a subshell. The l =...

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

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

Explore how heated gases produce line spectra, why hydrogen shows discrete wavelengths, and how Rydberg and Bohr helped explain emission lines.

Line Spectra from Heated Gases | 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。

Pennsylvania State Academic Standards

Earth and Space Science

Space Systems

3.3.9-12.B

3.3.9-12.C

Louisiana Student Standards for Science

High School

Earth Science

Earth’s Place In The Universe

HS-ESS1-1

HS-ESS1-2

motion-and-stability-forces-and-interactions

Motion And Stability: Forces And Interactions

HS-PS2-6

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Study Of Matter

Atoms

Tennessee Academic Standards

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

Waves and Their Applications in Technologies for Information Transfer

CHEM1.PS4.1

Virginia  Standards of Learning

HIgh School

CH.2

CH.2.e

PS.2

PS.2.a

Arizona Science Standards

HS+C.P1

HS+C.P1U1.2

Texas Essential Knowledge and Skills

CHEM.6

CHEM.6.A

CHEM.6.B

CHEM.6.C

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.1.c

Earth's Place in the Universe

9-12.ESS.1.1.b

9-12.ESS.1.2

9-12.ESS.1.2.c

9-12.ESS.1.3.a

Next Generation Science Standards

Earth’s Place in the Universe

Florida Department of Education

SC.912.E.5

SC.912.E.5.8

SC.912.P.8

SC.912.P.8.3

SC.912.P.10

SC.912.P.10.9

Physics

PHYS.8

PHYS.8.F

PHYS.9

PHYS.9.A

Chemistry and Physics

IPC.7

IPC.7.D

IPC.7.E

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

South Carolina College and Career Ready Science Standards

C-PS4-5

P-PS4-5

new-york-state-science-learning-standards

New York State Science Learning Standards

HS. Chemical Reactions

HS-PS1-7.

Georgia Standards of Excellence

SC1.

Light Emission and Electron Movement

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 ...

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 ...

Molecules and Compounds

Atoms and Molecules

Everything in the universe is made up of matter, and matter is composed of a combination of elements. An atom is the smallest unit of ...

Solution Formation

There is no one solvent that can dissolve every type of solute. Some substances that readily dissolve in a certain solvent might be insoluble in a ...

Colloids

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Construct an explanation to classify matter as a pure substance or mixture; homogeneous or heterogeneous; element or compound; solution, colloid or suspension.

PS.PSc.1.1

Phase Transitions

Whether solid, liquid, or gas, a substance&#39;s state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the ...

phase-transitions-vaporization-and-condensation

Phase Transitions: Vaporization and Condensation

The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize ...

Vapor Pressure

When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules move randomly about, they will occasionally ...

Clausius-Clapeyron Equation

The equilibrium between a liquid and its vapor depends on the temperature of the system; a rise in temperature causes a corresponding rise in the vapor ...

Phase Transitions: Melting and Freezing

Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy ...

phase-transitions-sublimation-and-deposition

Phase Transitions: Sublimation and Deposition

Some solids can transition directly into the gaseous state, bypassing the liquid state, via a process known as sublimation. At room temperature and ...

Heating and Cooling Curves

When a substance&#8212;isolated from its environment&#8212;is subjected to heat changes, corresponding changes in temperature and phase of the substance ...

Phase Diagrams

A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. ...

Use models to compare the phases of matter and the physical changes they undergo.

PS.PSc.1.2

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 ...

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

Carry out investigations to compare physical and chemical properties of matter.

PS.PSc.1.3

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 ...

The Bohr Model

Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded ...

Use models to interpret the data presented in Bohr diagrams and electron dot diagrams for neutral atoms of elements 1 through 18.

Understand types, properties, and structure of matter.

Line Spectra from Heated Gases

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