Transcript 3.7 Electron Energy Levels

Chapter 3 Atoms and Elements
3.7
Electron Energy Levels
Copyright © 2009 by Pearson Education, Inc.
1
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
nucleus.
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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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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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Orbitals
An s orbital
•has a spherical shape around the nucleus.
•is found in each energy level.
A p orbital
• has a two-lobed shape.
• is one of three p orbitals in each energy level from n = 2.
5
Orbitals
6
Electron Level Arrangement
In the electron level arrangement for the first 18
elements
• electrons are placed in energy levels (1, 2, 3, etc.),
beginning with the lowest energy level
• there is a maximum number in each energy level.
Energy level
Number of electrons
1
2 (up to He)
2
8 (up to Ne)
3
8 (up to Ar)
4
2 (up to Ca)
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Learning Check
Write the electron level arrangement for each:
1. N
2. Cl
3. K
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Solution
Write the electron level arrangement for each:
1. N
2, 5
2. Cl
2, 8, 7
3. K
2, 8, 8, 1
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Learning Check
Identify the element with each electron level
arrangement:
1. 2, 2
2. 2, 8, 3
3. 2, 7
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Solution
Identify the element with each electron level
arrangement:
1. Be
2, 2
2. Al
2, 8, 3
3. F
2, 7
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