Chapter 3 Atoms and Elements 3.6 Electron Energy Levels Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electromagnetic Spectrum The electromagnetic spectrum shows the arrangement of wavelengths of electromagnetic radiation, with the visible range from 700 to 400 nm. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Elements Have a Unique Atomic Spectrum When light from an element that is heated passes through a prism, it separates into a unique set of distinct lines of color called an atomic spectrum. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Energy Levels are assigned numbers n = 1, 2, 3, 4, and so on increase in energy as the value of n increases are like the rungs of a ladder, with the lower energy levels nearer the nucleus Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Energy Levels Energy levels have a maximum number of electrons equal to 2n2. Energy level Maximum number of electrons n = 1 2(1)2 = 2(1) = 2 n = 2 2(2)2 = 2(4) = 8 n = 3 2(3)2 = 2(9) = 18 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Changes in Electron Energy Level Electrons move to a higher energy level when it absorbs energy. When electrons fall back to a lower energy level, light is emitted. The energy emitted or absorbed is equal to the differences between the two energy levels. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Changes in Electron Energy Level Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements in Period 1 H 1 electron in 1st energy level. He 2 electrons in 1st energy level. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements in Period 2 Energy Level 1st 2nd Li 2 1 Be 2 2 B 2 3 C 2 4 N 2 5 O 2 6 F 2 7 Ne 2 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements in Period 3 Energy Level 1st 2nd 3rd Na 2 8 1 Mg 2 8 2 Al 2 8 3 Si 2 8 4 P 2 8 5 S 2 8 6 Cl 2 8 7 Ar 2 8 8 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements in Period 4 Energy Level 1st 2nd 3rd 4th K 2 8 8 1 Ca 2 8 8 2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Electron Arrangements Beyond 20 Energy Level 1st 2nd 3rd 4th 5th 6th 7th Number of Electrons 2 8 18 32 32 18 8 Electron arrangements are written as: O = 2,6 P = 2,8,5 Ca = 2,8,8,2 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Learning Check Write the electron arrangement for the following elements: C Si O N Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.

Solution Write the electron arrangement for the following elements: Si = 2,8,4 O = 2,6 N = 2,5 Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition Copyright © 2012 by Pearson Education, Inc.