1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

6. 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.

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

8. 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.

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

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

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

12. Electron Arrangements Beyond 20
Energy Level 1st 2nd rd th th 6th 7th
Number of
Electrons
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.

13. 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.

14. 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.