Chapter 5 Electrons In Atoms 5.3 Atomic Emission Spectra 5.1 Revising the Atomic Model 5.2 Electron Arrangement in Atoms 5.3 Atomic Emission Spectra and the Quantum Mechanical Model Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra The Nature of Light Light consists of electromagnetic waves. Amplitude - wave’s height from zero to the crest. Wavelength () - distance between the crests. Frequency () - number of wave cycles to pass a given point per unit of time. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra The Nature of Light Speed of Light = wavelength x frequency c = 2.998  108 m/s. c = ln Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra Frequency () and wavelength () are inversely proportional. As wavelength increases, frequency decreases. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculating the Wavelength of Light Sample Problem 5.2 Calculating the Wavelength of Light Calculate the wavelength of the yellow light emitted by a sodium lamp if the frequency of the radiation is 5.09 × 1014 Hz (5.09 × 1014/s). Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Sample Problem 5.2 c = ln Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the frequency of a red laser that has a wavelength of 676 nm? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the frequency of a red laser that has a wavelength of 676 nm? c = ln c   =  = = = 4.43  1014 m c 2.998  108 m/s  6.76  10–7 /s Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra The Nature of Light When sunlight passes through a prism, different wavelengths separate into a spectrum of colors. Red has the longest wavelength and lowest frequency. Violet has the shortest wavelength (highest frequency) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra Low energy ( = 700 nm) High energy ( = 380 nm) Frequency  (s-1) 3 x 106 3 x 1012 3 x 1022 102 10-8 10-14 Wavelength  (m) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra When atoms absorb energy, their electrons move to higher energy levels. These electrons lose energy by emitting light when they return to lower energy levels. No two elements have the same emission spectrum. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra Electrons orbit around the nucleus in specific energy levels (ground state) Electrons can absorb energy, become excited and move to a higher energy orbital (excited state) Excited electrons release energy as photons of light in order to get back to the ground state. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra A sample of H atoms receives energy from an external source. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra The excited atoms release energy by emitting photons. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Light and Atomic Emission Spectra Atomic Emission Spectra of Hydrogen Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The Quantum Concept and Photons The Quantization of Energy The amount of radiant energy (E) of a single quantum absorbed or emitted by a body is proportional to the frequency of radiation (n). h = Plank’s Constant = 6.626 x 10-34 J·s E = hn Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The Quantum Concept and Photons Photoelectric effect: electrons are ejected when light of sufficient frequency shines on a metal. Light quanta are called photons Energy of a photon = E = h x ⋎ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculating the Energy of a Photon Sample Problem 5.3 Calculating the Energy of a Photon What is the energy of a photon of microwave radiation with a frequency of 3.20 × 1011/s? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

E = h  = (6.626  10–34 J·s)  (3.20  1011/s) = 2.12  10–22 J Sample Problem 5.3 E = h  = (6.626  10–34 J·s)  (3.20  1011/s) = 2.12  10–22 J Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the frequency of a photon whose energy is 1.166  10–17 J? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the frequency of a photon whose energy is 1.166  10–17 J? E = h n n = h E  = = = 1.760  1016 Hz E 6.626  10–34 J h 1.166  10–17 J·s Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

END OF 5. 3 EM Waves https://www. youtube. com/watch END OF 5.3 EM Waves https://www.youtube.com/watch?v=cfXzwh3KadE Fireworks https://www.youtube.com/watch?v=nPHegSulI_M Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.