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Chapter 3 Atoms and Elements

3.7 Electron Energy Levels

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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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

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n=1

n=2

n=3

n=1

n=2

n=3

n=4

Atomic energylevels are like floors of a house

State transitions for the hydrogen atom

Creation of line spectrum for hydrogen

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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

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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.

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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

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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

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Atomic Orbitals for different n.

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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

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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

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The Orbital Model:Electronic Configurations

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First 20 Elements Electron Configurations

Neon (Ne)

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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.