1. Chapter 8 Covalent Bonding 8.2 The Nature of Covalent Bonding
8.1 Molecular Compounds
8.2 The Nature of Covalent
Bonding
8.3 Bonding Theories
8.4 Polar Bonds and Molecules
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2. The Octet Rule in Covalent Bonding
Single Covalent Bond: atoms held together by sharing one pair of electrons
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3. The Octet Rule in Covalent Bonding
Structural Formula: represents the covalent bonds as dashes and shows the arrangement of covalently bonded atoms.
H:H H-H
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4. The Octet Rule in Covalent Bonding
Unshared pair: pair of valence electrons that is not shared between atoms, also known as a lone pair (non-bonding pair).
In F2, each fluorine atom has three unshared pairs of electrons.
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5. The Octet Rule in Covalent Bonding
Double Covalent Bond: a bond that involves two shared pairs of electrons
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6. The Octet Rule in Covalent Bonding
Triple Covalent Bond: a bond formed by sharing three pairs of electrons
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7. Bond Dissociation Energies
Bond Dissociation Energy: energy required to break the bond between two covalently bonded atoms.
Bond
Bond Dissociation Energy
(kJ/mol)
Bond Length
(pm)
C C
347
154
C = C
657
133
908
121
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8. The Octet Rule in Covalent Bonding
Drawing Lewis Dot Structures:
Determine # of valence electrons.
Determine # of “octet” electrons.
*Note*– Hydrogen gets 2
# bonds = (# valence e- - # octet e-) / 2
Arrange atoms with # bonds from step 3.
Hydrogen & halogens bond one time
Group 6A elements bond 2 times
Group 5A elements bond 3 times
Carbon always bonds 4 times
Add electron pairs until all atoms have the correct number of electrons around them
Recheck your answer.
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9. The Octet Rule in Covalent Bonding
Draw Lewis Dot Structures for each molecular compound:
SiO2
HCl
H2O
HCN
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10. Exceptions to the Octet Rule
Molecules whose total number of valence electrons is an odd number.
2. Boron wants 6 electrons for neutral molecules.
3. Phosphorus and sulfur expand the octet to 10 or 12 electrons.
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11. The ozone molecule has two possible electron dot structures.
Resonance
Resonance structures: structures that occur when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion.
The ozone molecule has two possible electron dot structures.
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12. http://www. pbslearningmedia. org/resource/ess05. sci. ess. watcyc
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13. What is ozone and what causes its depletion?
What are the benefits and disadvantage of ozone?
What are the implications of a depleted ozone layer?
Create a timeline of major milestones related to ozone depletion.
What challenges do you think arise when confronting an emerging environmental issue?
What are other examples of humans affecting our environment?
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14. END OF 8.2
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