1. Chapter 7 Ionic and Metallic Bonding 7.2 Ionic Bonds and
7.1 Ions
7.2 Ionic Bonds and
Ionic Compounds
7.3 Bonding in Metals
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2. Where does table salt come from?
CHEMISTRY & YOU
Where does table salt come from?
In some countries, salt is obtained by the evaporation of seawater. In other countries, salt is mined from rock deposits deep underground.
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3. Formation of Ionic Compounds
What is the electrical charge of an ionic compound?
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4. Formation of Ionic Compounds
Sodium chloride, or table salt, is an ionic compound consisting of sodium cations and chloride anions.
An ionic compound is a compound composed of cations and anions.
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5. Formation of Ionic Compounds
Although they are made of ions, ionic compounds are electrically neutral.
The total positive charge of the cations equals the total negative charge of the anions.
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6. Formation of Ionic Compounds
Ionic Bonds
The electrostatic forces that hold ions together in ionic compounds are called ionic bonds.
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7. Formation of Ionic Compounds
Ionic Bonds
When sodium and chlorine react to form a compound, the sodium atom transfers its one valence electron to the chlorine atom.
Sodium and chlorine atoms combine in a one-to-one ratio, and both ions have stable octets.
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8. Formation of Ionic Compounds
Ionic Bonds
Aluminum metal (Al) and the nonmetal bromine (Br2) react violently to form the ionic solid aluminum bromide (AlBr3).
Each bromine atom has seven valence electrons and readily gains one additional electron.
Three bromine atoms combine with each aluminum atom.
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9. Formation of Ionic Compounds
Formula Units
A chemical formula shows the numbers of atoms of each element in the smallest representative unit of a substance.
NaCl is the chemical formula for sodium chloride.
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10. Formation of Ionic Compounds
Formula Units
Ionic compounds do not exist as discrete units, but as collections of positively and negatively charged ions arranged in repeating patterns.
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11. Formation of Ionic Compounds
Formula Units
The chemical formula of an ionic compound refers to a ratio known as a formula unit.
A formula unit is the lowest whole-number ratio of ions in an ionic compound.
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12. Formation of Ionic Compounds
Formula Units
For sodium chloride, the lowest whole-number ratio of the ions is 1:1 (one Na+ ion to each Cl– ion).
The formula unit for sodium chloride is NaCl.
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13. Predicting Formulas of Ionic Compounds
Sample Problem 7.1
Predicting Formulas of Ionic Compounds
Use electron dot structures to predict the formulas of the ionic compounds formed from the following elements:
a. potassium and oxygen
b. magnesium and nitrogen
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14. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
a. Start with the atoms.
• • •
K and O
• • • •
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15. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
a. In order to have a completely filled valence shell, the oxygen atom must gain two electrons. These electrons come from two potassium atoms, each of which loses one electron. K •
• • O + K+ 2–
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16. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
a. Express the electron dot structure as a formula.
The formula of the compound formed is K2O (potassium oxide).
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17. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
b. Start with the atoms.
Mg and N •
• •
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18. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
b. Each nitrogen atom needs three electrons to have an octet, but each magnesium atom can lose only two electrons. Three magnesium atoms are needed for every two nitrogen atoms. •
• • N 3– +
Mg2+ Mg
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19. Solve Apply the concepts to this problem.
Sample Problem 7.1
Solve Apply the concepts to this problem. 2
b. Express the electron dot structure as a formula.
The formula of the compound formed is Mg3N2 (magnesium nitride).
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20. Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine.
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21. Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine.
• • F • +
Ca2+ – Ca
CaF2
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22. Properties of Ionic Compounds
What are three properties of ionic compounds?
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23. Properties of Ionic Compounds
Most ionic compounds are crystalline solids at room temperature.
The component ions in such crystals are arranged in repeating three-dimensional patterns.
The beauty of crystalline solids comes from the orderly arrangement of their component ions.
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24. Properties of Ionic Compounds
Ionic compounds generally have high melting points.
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25. Properties of Ionic Compounds
Ionic compounds can conduct an electric current when melted or dissolved in water.
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26. Properties of Ionic Compounds
When sodium chloride is melted, the orderly crystal structure breaks down.
To (+) electrode
To (–) electrode
Inert metal electrodes
Flow of electrons
Current meter
Power source
Cl–
Na+
If a voltage is applied across this molten mass, cations migrate freely to one electrode and anions migrate to the other.
This movement of electrons allows electric current to flow between the electrodes through an external wire.
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27. Properties of Ionic Compounds
This solar facility uses molten NaCl for its ability to absorb and hold a large quantity of heat, which is used to generate electricity.
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28. Properties of Ionic Compounds
Ionic compounds also conduct electric current if they are dissolved in water.
When dissolved, the ions are free to move about in the solution.
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29. When can ionic compounds conduct an electric current?
A. Only when melted
B. When melted or dissolved in water
C. Only when dissolved in water
D. When solid or melted
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30. When can ionic compounds conduct an electric current?
A. Only when melted
B. When melted or dissolved in water
C. Only when dissolved in water
D. When solid or melted
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31. Questions What is the electrical charge on an ionic compound?
What is an ionic bond?
What does a chemical formula show?
Write the chemical formula for the compound that is formed when:
a. calcium reacts with oxygen
b. sodium reacts with nitrogen
c. potassium reacts with sulfur
5. What are three properties of ionic compounds?
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32. ionic compound: a compound composed of positive and negative ions
Glossary Terms
ionic compound: a compound composed of positive and negative ions
ionic bond: the electrostatic attraction that binds oppositely charged ions together
chemical formula: an expression that indicates the number and type of atoms present in the smallest representative unit of a substance
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33. Glossary Terms
formula unit: the lowest whole-number ratio of ions in an ionic compound; in magnesium chloride, the ratio of magnesium ions to chloride ions is 1:2 and the formula unit is MgCl2
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