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. Formation of Ionic Compounds
Cations + Anions
Electrically neutral
- Total positive charge = Total negative charge
Subscripts indicate lowest whole number ratio of ions in the formula unit
- examples: NaCl, CaCl2
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3. Formation of Ionic Compounds
Ionic Bonds - NaCl
The sodium atom transfers one valence electron to the chlorine atom.
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4. Formation of Ionic Compounds
What ionic compound do you think would form between the following elements?
a) Potassium and Oxygen
b) Magnesium and Nitrogen
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5. Oxygen must gain two electrons. Each potassium loses one electron.
Sample Problem 7.1
Oxygen must gain two electrons.
Each potassium loses one electron. K •
• • O + K+ 2–
The formula of the compound formed is K2O.
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6. The formula of the compound is Mg3N2.
Sample Problem 7.1
b. Each nitrogen needs three electrons to have an octet. Each magnesium atom can lose only two electrons. •
• • N 3– +
Mg2+ Mg
The formula of the compound is Mg3N2.
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7. Properties of Ionic Compounds
Most are crystalline solids
at room temperature.
High Melting Points
Composed of a metal & nonmetal
Can conduct electric current when melted or dissolved in water
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8. Formation of Ionic Compounds
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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9. Formation of Ionic Compounds
The structure of an ionic compound is called a crystalline structure.
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10. Formation of Ionic Compounds
Formula Units
Lowest whole number ratio of ions in an ionic compound.
The formula unit for sodium chloride is NaCl.
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11. 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+
This movement of electrons allows electric current to flow between the electrodes through an external wire.
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12. Properties of Ionic Compounds
Ionic compounds conduct electric current when dissolved in water.
When dissolved, the ions are free to move about in the solution.
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13. END OF 7.2
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