Transcript CH_4_1_Octet_Rule_and_Ions

Chapter 4
Compounds and Their Bonds
1
4.1
Octet Rule and Ions
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Ionic and Covalent Bonds
2
Atoms that are not noble gases form octets
•
to become more stable
•
by losing, gaining, or sharing valence electrons
•
by forming ionic bonds or covalent bonds
Ionic bonds occur when atoms of one element lose
valence electrons and the atoms of another element
gain valence electrons.
Covalent bonds occur when nonmetal atoms share
electrons to attain a noble gas arrangement.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
The Octet Rule
3
An octet
• is eight valence electrons
• is associated with the stability of the noble gases
(except He)
The octet rule states that elements gain or lose electrons
and become ions to attain noble gas arrangement.
valence electrons
He 2
2
Ne 2, 8
8
Ar
8
Kr
2, 8, 8
2, 8, 14, 8
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
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Ionic and Covalent Bonds
4
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Metals Form Positive Ions
5
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+
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formation of Magnesium Ion, Mg2+
6
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Nonmetals Form Negative Ions
7
Nonmetals form negative ions:
• by a gain of valence electrons
• with the electron configuration of the nearest noble gas
• with fewer protons than electrons
Group 5A nonmetals ion 3−
Group 6A nonmetals ion 2−
Group 7A nonmetals ion 1−
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formation of Chloride Ion, Cl−
8
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Formulas and Names of Common Ions
9
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
10
Write the formula and symbol of an ion with 16 protons and 18
electrons.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
11
Write the formula and symbol of an ion with 16 protons and 18
electrons.
The element with 16 protons is sulfur, with the symbol S.
An ion of sulfur with 18 electrons gives sulfur a charge of 2−.
The sulfide ion is S2−.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Ionic Charges from Group Numbers
12
Group
Charge
Group 1A
Group 2A
Group 3A
1+
2+
3+
Positive Charges
Group 5A
Group 6A
Group 7A
3−
2−
1−
Negative Charges
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Ionic Charges from Group Numbers
13
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
14
Consider the elements calcium and chlorine.
A. Identify each as a metal or a nonmetal.
B. State the number of valence electrons for each.
C. State the number of electrons that must be lost or
gained for each to acquire an octet.
D. Write the symbol, including its ionic charge, and
name of each resulting ion.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
15
Consider the elements calcium and chlorine.
A. Identify each as a metal or a nonmetal.
metal = calcium
nonmetal = chlorine
B. State the number of valence electrons for each.
Calcium has two valence electrons.
Chlorine has seven valence electrons.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
16
C. State the number of electrons that must be lost or
gained for each to acquire an octet.
Calcium will lose 2 electrons to acquire an octet.
Chlorine will gain 1 electron to acquire an octet.
D. Write the symbol, including its ionic charge, and
name of each resulting ion.
Ca2+ calcium
Cl− chloride
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.