Understanding Covalent Bonds in Molecular Compounds

1. Chemistry 8.2

2. 8.1 Molecules and Molecular Compounds Bell Work How would you combine the following: Ca2+ PO43-

3. 8.1 Molecules and Molecular Compounds • A molecule: atoms joined together by covalent bonds (shared). Neutral. • A diatomic molecule: a molecule consisting of two atoms. Rule of 7’s.

4. 8.1 Molecules and Molecular Changes • Molecular compounds tend to have relatively lower melting and boiling points than ionic compounds.

5. 8.2 The Octet Rule in Covalent Bonding • Molecules are made up of non-metals held together by covalent bonds.

6. Which of the following has the highest melting point? a) NO2 b) CaBr2 c) CH4

7. 8.2 The Octet Rule in Covalent Bonding • In covalent bonds, atoms SHARE electrons to obtain noble gas electron configurations.

8. 8.2 Single Covalent Bonds • Single Covalent Bonds • How can we show covalent bonds with electron dot structures?

9. 8.2 Single Covalent Bonds • Two atoms held together by sharing a pair of electrons are joined by a single covalent bond.

10. 8.2 Single Covalent Bonds • An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots. • A structural formula represents the covalent bonds by dashes (H-H) and shows the arrangement of covalently bonded atoms.

11. 8.2 Single Covalent Bonds • The halogens form single covalent bonds in their diatomic molecules. Fluorine is one example.

12. 8.2 Single Covalent Bonds • A pair of valence electrons that is not shared between atoms is called an unshared pair or Lone Pair.

13. 8.1 Section Assessment

14. 8.1 Section Assessment

15. 8.2 Double and Triple Covalent Bonds • A bond that involves two shared pairs of electrons is a double covalent bond. • A bond formed by sharing three pairs of electrons is a triple covalent bond.

16. 8.2 Double and Triple Covalent Bonds

17. 8.2 Coordinate Covalent Bonds • Coordinate Covalent Bonds • How are coordinate covalent bonds different from other covalent bonds?

18. 8.2 Coordinate Covalent Bonds • In carbon monoxide, oxygen has a stable configuration but the carbon does not.

19. 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.

20. 8.2 Coordinate Covalent Bonds • A coordinate covalent bond is a covalent bond in which one atom contributes both bonding electrons. • Shown by arrows

21. 8.2 Coordinate Covalent Bonds • A polyatomic ion, such as NH4+, is a tightly bound group of atoms that has a positive or negative charge and behaves as a unit. • Most plants need nitrogen that is already combined in a compound to grow.

22. 8.2 Coordinate Covalent Bonds

23. 8.2 Section Assessment

24. 8.2 Section Assessment

25. 8.2 Bond Dissociation Energies • Bond Dissociation Energies • How is the strength of a covalent bond related to its bond dissociation energy?

26. 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.

27. 8.2 Section Quiz. • 8.2.

28. 8.2 Section Quiz. • 1. In covalent bonding, atoms attain the configuration of noble gases by • losing electrons. • gaining electrons. • transferring electrons. • sharing electrons.

29. 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.

30. 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

31. END OF SHOW