1. Chapter 4 Compounds and Their Bonds
4.1
Octet Rule and Ions
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2. Octet Rule An octet is 8 valence electrons.
is associated with the stability of the noble gases.
He is stable with 2 valence electrons (duet).
valence electrons He
Ne 2,
Ar 2, 8,
Kr 2, 8, 14,

3. Ionic and Covalent Bonds
Atoms form octets
to become more stable.
by losing, gaining, or sharing valence electrons.
by forming ionic bonds or covalent bonds.
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4. Metals Form Positive Ions
by a loss of their valence electrons.
with the electron configuration of the nearest noble gas.
that have fewer electrons than protons.
Group 1A metals  ion 1+
Group 2A metals  ion 2+
Group 3A metals  ion 3+
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5. Formation of a Sodium Ion, Na+
Sodium achieves an octet by losing its one valence
electron.
2, 8, 1
2, 8
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6. Charge of Sodium Ion, Na+
With the loss of its valence electron,
the sodium ion has a +1 charge.
Sodium atom Sodium ion
11p p+
11e e-
2, 8
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7. Formation of Mg2+
Magnesium achieves an octet by losing its two valence electrons.
2, 8, 2
2, 8
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8. Charge of Magnesium Ion Mg2+
With the loss of two valence
Electrons, magnesium forms a
positive ion with a +2 charge.
Mg atom Mg2+ ion
12p+ 12p+
12e e-
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9. Learning Check A. The number of valence electrons in aluminum is
1) 1e ) 2e-. 3) 3e-.
B. The change in electrons for octet requires a
1) loss of 3e ) gain of 3e ) a gain of 5e-.
C. The ionic charge of aluminum is
1) ) ) 3+.
D. The symbol for the aluminum ion is
1) Al3+. 2) Al3-. 3) Al+.

10. Solution A. The number of valence electrons in aluminum is 3) 3 e-.
B. The change in electrons for octet requires a
1) loss of 3e-.
C. The ionic charge of aluminum is
3) 3+.
D. The symbol for the aluminum ion is
1) Al3+.

11. Formation of Negative Ions
In ionic compounds, nonmetals
achieve an octet arrangement.
gain electrons.
form negatively charged ions with 3-, 2-, or 1- charges.

12. Formation of a Chloride, Cl-
Chlorine achieves an octet by adding an electron to its valence electrons.
2, 8, 7
2, 8, 8
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13. Charge of a Chloride Ion, Cl-
By gaining one electron, the chloride ion has a -1 charge.
Chlorine atom Chloride ion
17p p+
17e e- –
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14. Ionic Charge from Group Numbers
The charge of a positive ion is equal to its Group number.
Group 1A(1) = 1+
Group 2A(2) = 2+
Group 3A(3) = 3+
The charge of a negative ion is obtained by subtracting 8 or 18 from its Group number.
Group 6A(16) = = 2-
or = 2-

15. Some Ionic Charges I- Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings

16. Learning Check A. The number of valence electrons in sulfur is
1) 4e ) 6e ) 8e-.
B. The change in electrons for octet requires a
1) loss of 2e ) gain of 2e-. 3) a gain of 4e-.
C. The ionic charge of sulfur is
1) ) ) 4-.

17. Solution A. The number of valence electrons in sulfur is 2) 6e-.
B. The change in electrons for octet requires a
2) gain of 2e-.
C. The ionic charge of sulfur is
2) 2-.