Transcript Chapter 2 Atoms and Elements

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
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Energy levels are spaced differently, like
ladder rungs
n=4
n=3
n=3
n=2
n=1
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n=2
n=1
Atomic energy
levels are like floors of a house
State transitions for the
hydrogen atom
Creation of line spectrum for
hydrogen
Energy Levels
Energy levels have a maximum number of electrons
equal to 2n2.
Energy level
n=1
n=2
n=3
Maximum number of electrons
2(1)2 = 2(1) = 2
2(2)2 = 2(4) = 8
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.
n=3
n=2
n=1
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
9
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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Learning Check
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.
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Solution
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.
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Sample energy level diagram
The Orbital Model:
Electronic Configurations
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First 20 Elements Electron Configurations
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Neon (Ne)
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.
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