Transcript 9.6

Chapter 9 Electron
Configuration and Periodic
Trends
9.6
Periodic Trends of the Elements
1
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Valence Electrons
The valence electrons
• Determine the chemical properties of the elements.
• Are the electrons in the s and p sublevels in the
highest energy level.
• Are related to the Group number of the element.
Example: Phosphorus has 5 valence electrons
5 valence electrons
P Group 5A(15)
2
1s22s22p6 3s23p3
Group Number and Valence
Electrons
All the elements in a group have the same number
of valence electrons.
Example:
Elements in Group 2A(2) have two (2) valence
electrons.
Be
1s2 2s2
Mg
1s2 2s2 2p6 3s2
Ca
1s2 2s2 2p6 3s2 3p6 4s2
Sr
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2
3
Periodic Table and Valence
Electrons
Table 9.3
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4
Learning Check
State the number of valence electrons for each:
A. O
1) 4
2) 6
3) 8
5
B. Al
1) 13
2) 3
3) 1
C. Cl
1) 2
2) 5
3) 7
Solution
State the number of valence electrons for each.
A. O
2) 6
B. Al
2) 3
C. Cl
3) 7
6
Learning Check
State the number of valence electrons for each.
A. Calcium
1) 1
2) 2
3) 3
B. Group 6A (16)
1) 2
2) 4
3) 6
C. Tin
1) 2
2) 4
3) 14
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Solution
State the number of valence electrons for each.
A. Calcium
2) 2
B. Group 6A (16)
3) 6
C. Tin
2) 4
8
Learning Check
State the number of valence electrons for each.
A. 1s2 2s2 2p6 3s2 3p3
B. 1s2 2s2 2p6 3s2 3p64s2 3d104p4
C. 1s22s22p5
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Solution
State the number of valence electrons for each.
A. 1s2 2s2 2p6 3s2 3p3
5
B. 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p4
6
C. 1s22s22p5
7
10
Atomic Size
Atomic radius
•Is the distance from the nucleus to the valence
electrons.
11
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Atomic Radius Within A Group
Atomic radius increases
• Going down each
group of
representative
elements.
• As the number of
energy levels
increases.
12
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Atomic Radius Across a Period
Atomic radius decreases
• Going from left to right across a period.
• As more protons increase nuclear attraction
for valence electrons.
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13
Learning Check
Select the element in each pair with the larger
atomic radius.
A.
B.
C.
14
Li or K
K or Br
P or Cl
Solution
Select the element in each pair with the larger
atomic radius.
A. K
B. K
C. P
15
Sizes of Metal Atoms and Ions
A positive ion
• Has lost its
valence electrons.
• Is smaller (about
half the size) than
its corresponding
metal atom.
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16
Size of Sodium Ion
The sodium ion Na+
• Forms when the Na atom loses one electron
from the 3rd energy level.
• Is smaller than a Na atom.
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17
Sizes of Nonmetal Atoms and
Ions
A negative ion
• Has a complete octet.
• Increases the number of
valence electrons.
• Is larger (about twice the
size) than its
corresponding metal
atom.
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18
Size of Fluoride Ion
The fluoride ion F• Forms when a valence electron is added.
• Has increased repulsions due to the added
valence electron.
• Is larger than F atom
19
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Learning Check
1. Which is larger in each of the following?
A. K or K+
B. Al or Al3+
C. S2- or S
2. Which is smaller in each of the following?
A. N3- or N
B. Cl or ClC. Sr2+ or Sr
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Solution
1. Which is larger in each of the following?
A. K > K+
B. Al > Al3+
C. S2- > S
2. Which is smaller in each of the following?
A. N < N3B. Cl < ClC. Sr2+< Sr
21
Ionization Energy
Ionization energy
• Is the energy it takes to remove a valence electron.
Na(g) + Energy of
Ionization
Na+(g)
+
e-
+
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22
Ionization Energy
Metals have
• 1-3 valence
electrons.
• Lower
ionization
energies.
23
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Ionization Energy
Nonmetals have
• 5-7 valence
electrons.
• Have higher
ionization
energies.
24
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Ionization Energy
Nobel gases have
• Complete octets
(He has two
valence
electrons.)
• Have the highest
ionization
energies in each
period.
25
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Learning Check
Select the element in each pair with the higher
Ionization energy.
A.
B.
C.
26
Li or K
K or Br
P or Cl
Solution
Select the element in each pair with the higher
Ionization energy.
A.
B.
C.
27
Li
Br
Cl