Ch.6 - Electronic Structure of Atoms

Brown - Chemistry: The Central Science 14th Edition

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Brown 14th Edition

Ch.6 - Electronic Structure of Atoms

Problem 83a

Chapter 6, Problem 83a

Certain elements emit light of a specific wavelength when they are burned or heated in a non-luminous flame. Historically, chemists used such emission wavelengths to determine whether specific elements were present in a sample. Some characteristic wavelengths for a few of the elements are given in the following table: Ag 328.1 nm Fe 372.0 nm Au 267.6 nm K 404.7 nm Ba 455.4 nm Mg 285.2 nm Ca 422.7 nm Na 589.6 nm Cu 324.8 nm Ni 341.5 nm (a) Determine which of these emissions occur in the ultraviolet part of the spectrum.

Verified step by step guidance

Understand the electromagnetic spectrum: The electromagnetic spectrum includes different types of radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The ultraviolet (UV) region is typically defined as having wavelengths from about 10 nm to 400 nm.

Identify the given wavelengths: The problem provides specific wavelengths for different elements: Ag (328.1 nm), Fe (372.0 nm), Au (267.6 nm), K (404.7 nm), Ba (455.4 nm), Mg (285.2 nm), Ca (422.7 nm), Na (589.6 nm), Cu (324.8 nm), and Ni (341.5 nm).

Compare each wavelength to the UV range: Check if each given wavelength falls within the UV range of 10 nm to 400 nm.

List the elements with UV emissions: For each element, if its wavelength is less than or equal to 400 nm, it emits in the UV region. Identify these elements.

Summarize the findings: Provide a list of elements whose emission wavelengths fall within the UV range, based on the comparison in the previous step.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Electromagnetic Spectrum

The electromagnetic spectrum encompasses all types of electromagnetic radiation, arranged by wavelength. It includes gamma rays, X-rays, ultraviolet (UV) light, visible light, infrared radiation, and radio waves. The UV region ranges from about 10 nm to 400 nm, which is crucial for identifying the wavelengths of emitted light from elements.

Emission Spectra

Emission spectra are produced when atoms or molecules emit light at specific wavelengths after being energized. Each element has a unique emission spectrum, which serves as a 'fingerprint' for identifying the presence of that element in a sample. The emitted light can be analyzed to determine the wavelengths corresponding to different elements.

Wavelength and Energy Relationship

The energy of electromagnetic radiation is inversely related to its wavelength, described by the equation E = hc/λ, where E is energy, h is Planck's constant, c is the speed of light, and λ is the wavelength. Shorter wavelengths, such as those in the UV range, correspond to higher energy emissions, which is essential for understanding which emissions fall within the UV spectrum.

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Related Practice

Textbook Question

If a sample of calcium chloride is introduced into a nonluminous flame, the color of the flame turns to orange (“flame test”). The light is emitted because calcium atoms become excited; their return to the ground state results in light emission. (c) Calculate the energy gap between the excited and ground states for the calcium atom.

Textbook Question

In January 2006, the New Horizons space probe was launched from Earth with the mission to perform a flyby study of Pluto. The arrival at the dwarf planet was estimated to happen after nine years, in 2015. The distance between Earth and Pluto varies depending on the location of the planets in their orbits, but at their closest, the distance is 4.2 billion kilometers (2.6 billion miles). Calculate the minimum amount of time it takes for a transmitted signal from Pluto to reach the Earth.

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Textbook Question

The watt is the derived SI unit of power, the measure of energy per unit time: 1 W = 1 J>s. A semiconductor laser in a DVD player has an output wavelength of 650 nm and a power level of 5.0 mW. How many photons strike the DVD surface during the playing of a DVD 90 minutes in length?

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Textbook Question

Consider the two waves shown here, which we will consider to represent two electromagnetic radiations: (b) What is the frequency of wave A?

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Textbook Question

If a sample of calcium chloride is introduced into a nonluminous flame, the color of the flame turns to orange ('flame test'). The light is emitted because calcium atoms become excited; their return to the ground state results in light emission. (b) What is the energy of 1.00 mol of these photons (a mole of photons is called an Einstein)?

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