## Structure 1.3.1—Emission spectra are produced by atoms emitting photons when electrons in excited states return to lower energy levels.

Structure 1.3.1—Emission spectra are produced by atoms emitting photons when electrons in excited states return to lower energy levels.

What You’ll Learn:

• Qualitatively describe the relationship between colour, wavelength, frequency and energy across the electromagnetic spectrum.
• Distinguish between a continuous and a line spectrum.

Keywords

Emission spectra are produced when atoms emit photons as their electrons transition from higher energy states to lower energy states. This process can be better understood through the following concepts:

1. Electromagnetic spectrum: The electromagnetic spectrum consists of a range of electromagnetic waves with varying wavelengths, frequencies, and energies. This spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Visible light, which ranges from approximately 400 nm (violet) to 700 nm (red), is the part of the spectrum that human eyes can perceive as colors.
2. The relationship between color, wavelength, frequency, and energy: The color of light depends on its wavelength. Shorter wavelengths correspond to higher frequencies and higher energies, while longer wavelengths correspond to lower frequencies and lower energies. The relationship between wavelength (λ) and frequency (ν) is given by the equation c = λν, where c is the speed of light. Energy (E) is related to frequency by the equation E = hν, where h is Planck’s constant.

In the visible spectrum, violet light has the shortest wavelength, highest frequency, and highest energy, while red light has the longest wavelength, lowest frequency, and lowest energy. The order of colors in the visible spectrum from highest to lowest energy is: violet, blue, green, yellow, orange, and red.

1. Continuous and line spectra: A continuous spectrum is an unbroken band of colors that includes all the wavelengths within a specific range. When white light is passed through a prism, a continuous spectrum is produced, consisting of all the colors of the visible spectrum. This occurs because white light is a combination of all the colors in the visible range.

In contrast, a line spectrum, also known as an atomic emission spectrum, consists of discrete lines of specific colors (wavelengths) corresponding to the unique energy levels of a particular element. When an element is heated or subjected to an electric discharge, its electrons are excited to higher energy levels. As the electrons return to their lower energy states, they emit photons with energies specific to the energy level transitions. These emitted photons correspond to specific wavelengths, which appear as distinct colored lines when the emitted light is passed through a spectrometer.

In summary, emission spectra are produced when atoms emit photons as their electrons transition from excited states to lower energy levels. The color, wavelength, frequency, and energy of these photons are interconnected, with shorter wavelengths corresponding to higher frequencies and energies. Continuous spectra contain an unbroken range of wavelengths, while line spectra consist of discrete lines that correspond to the unique energy levels of a specific element.

Questions

1. What causes emission spectra to be produced in atoms, and how are they related to electron transitions?
2. How are color, wavelength, frequency, and energy interrelated in the context of the electromagnetic spectrum?
3. What is the order of colors in the visible spectrum from highest to lowest energy, and how do their wavelengths and frequencies correspond?
4. What is the difference between a continuous spectrum and a line spectrum, and how are they produced?
5. How does the atomic emission spectrum reveal information about the unique energy levels of a specific element?