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. Group in Periodic Table Will if form a Cation or Anion?
CHEMISTRY & YOU
Do Now:
Complete the table below in your notebook.
Element
Group in Periodic Table
# of Valence
Electrons
Will if form a Cation or Anion?
Ionic Charge? Li I S Ca N
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3. Group in Periodic Table Will if form a Cation or Anion?
CHEMISTRY & YOU
Do Now:
Complete the table below.
Element
Group in Periodic Table
# of Valence
Electrons
Will if form a Cation or Anion?
Ionic Charge? Li 1A 1
Cation 1+ I 7A 7
Anion 1- S 6A 6 2- Ca 2A 2 2+ N 5A 5 3-
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4. Formation of Ionic Compounds
Composed of cations & anions.
Electrically neutral
- Total positive charge = Total negative charge
Ions held together by ionic bonds
- electrostatic forces (opposite charges attract)
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5. Formation of Ionic Compounds
What happens when Sodium and Chloride react?
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6. Formation of Ionic Compounds
Ionic Bonds - NaCl
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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7. 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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8. The formula of the compound formed is K2O.
Sample Problem 7.1
a. In order to have a 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–
The formula of the compound formed is K2O.
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9. The formula of the compound is Mg3N2.
Sample Problem 7.1
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
The formula of the compound is Mg3N2.
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10. 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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11. 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.
Although ionic charges are used to derive the correct formula, they are not shown when you write the formula unit of the compound.
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12. 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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13. Formation of Ionic Compounds
The structure of an ionic compound is called a crystalline structure.
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14. Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine.
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15. Use electron dot structures to determine the formula of the ionic compound formed when calcium reacts with fluorine.
• • F • +
Ca2+ – Ca
The formula is CaF2.
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16. Properties of Ionic Compounds
Most ionic compounds are crystalline solids at room temperature.
High Melting Points
Can conduct electric current when melted or dissolved in water
Composed of a metal & nonmetal
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17. 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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18. 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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19. END OF 7.2
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