1 Chapter 3 Atoms and Elements 3.7 Electron Energy Levels Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

2 Energy Levels 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 ground. n = 4 n = 3 n = 2 n = 1

Energy levels are spaced differently, like rungs of a ladder Credit: Foto-Search.com n=1 n=2 n=3 n=1 n=2 n=3 n=4

Atomic energy levels are like floors of a house

State transitions for the hydrogen atom

Creation of line spectrum for hydrogen

7 Energy Levels Energy levels have a maximum number of electrons equal to 2n 2. Energy levelMaximum number of electrons n = 12(1) 2 = 2(1) = 2 n = 22(2) 2 = 2(4) = 8 n = 32(3) 2 = 2(9) = 18

8 Atomic Orbitals An orbital is a three-dimensional space around a nucleus where an electron is most likely to be found. has a shape that represents electron density (not a path the electron follows). can hold up to 2 electrons.

9 s Orbitals An s orbital has a spherical shape around the nucleus. is found in each energy level. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings n = 1 n = 2 n = 3

10 p Orbitals A p orbital has a two-lobed shape. is one of three p orbitals in each energy level from n = 2. Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings

11 Atomic Orbitals for different n.

12 The number of A. electrons that can occupy a p orbital is 1) 1.2) 2.3) 3. B. p orbitals in the 2p sublevel is 1) 1.2) 2.3) 3. C. electrons in the n =3 level 1) 3.2) 6.3) 18. Learning Check

13 The number of A. electrons that can occupy a p orbital is 2) 2. B. p orbitals in the 2p sublevel is 3) 3. C. electrons in the n =3 level 3) 18. Solution

Sample energy level diagram

15 The Orbital Model: Electronic Configurations

16 First 20 Elements Electron Configurations

Neon (Ne)

18 Neon, a partially evacuated tube that contains neon gas gives a reddish-orange glow when high voltage is applied. The line emission spectrum of neon is obtained when light from a neon source passes through a prism.