Single Covalent Bonds

1. 8.2 Single Covalent Bonds • B. The nature of Covalent Bonding • 1. The Octet Rule: electron sharing occurs so that atoms attain the electron configurations of noble gases. • 2. Bond Representation: • a. Single Bond: Two atoms held together by sharing a pair of electrons. • b. Electron dot structure of a bond: • H:H or H-H

2. 8.2 Single Covalent Bonds • c. Halogens form single covalent bonds in their diatomic molecules. Example: Fluorine • 3. unshared pair: pairs of valence electrons that are not shared between atoms a. The ammonia molecule has one unshared pair of electrons.

3. 8.2 Single Covalent Bonds • Hydrogen and oxygen atoms attain noble-gas configurations by sharing electrons. a. Note H’s & the O now have full orbitals

4. 8.2 Single Covalent Bonds • 5. Methane has no unshared pairs of electrons. • PRACTICE:

5. 8.2 Double and Triple Covalent Bonds • 6. Multiple Bonds: • a. Double covalent bond: A bond that involves two shared pairs of electrons. • b. Triple covalent bond: A bond formed by sharing three pairs of electrons. • (Example of a double Bond)

6. 8.2 Double and Triple Covalent Bonds

7. 8.2 Double and Triple Covalent Bonds • Carbon dioxide is an example of a triatomic molecule.

8. 8.2 Coordinate Covalent Bonds • Coordinate Covalent Bonds • How are coordinate covalent bonds different from other covalent bonds?

9. 8.2 Coordinate Covalent Bonds • As shown below, the dilemma is solved if the oxygen donates one of its unshared pairs of electrons for bonding.

10. 8.2 Coordinate Covalent Bonds • A coordinate covalent bond is a covalent bond in which one atom contributes both bonding electrons. • In a structural formula, you can show coordinate covalent bonds as arrows that point from the atom donating the pair of electrons to the atom receiving them.

11. 8.2 Coordinate Covalent Bonds

12. 8.2 Bond Dissociation Energies • Bond Dissociation Energies • How is the strength of a covalent bond related to its bond dissociation energy?

13. 8.2 Bond Dissociation Energies • The energy required to break the bond between two covalently bonded atoms is known as the bond dissociation energy. • A large bond dissociation energy corresponds to a strong covalent bond.

14. 8.2 Resonance • A resonance structure is a structure that occurs 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.

15. 8.2 Exceptions to the Octet Rule • Exceptions to the Octet Rule • What are some exceptions to the rule?

16. 8.2 Exceptions to the Octet Rule • Two electron dot structures can be drawn for the NO2 molecule.

17. 8.2 Exceptions to the Octet Rule • The electron dot structure for PCl5 can be written so that phosphorus has ten valence electrons.

18. 8.2 Section Quiz. • 1. In covalent bonding, atoms attain the configuration of noble gases by • losing electrons. • gaining electrons. • transferring electrons. • sharing electrons.

19. 8.2 Section Quiz • 2. Electron dot diagrams are superior to molecular formulas in that they • show which electrons are shared. • indicate the number of each kind of atom in the molecule. • show the arrangement of atoms in the molecule. • are easier to write or draw.

20. 8.2 Section Quiz • 3. Which of the following molecules would contain a bond formed when atoms share three pairs of electrons? • Se2 • As2 • Br2 • Te2