2. Review Write the electron configuration for an atom of carbon and chlorine. Determine the empirical and molecular formula for a compound consisting of 7.8% carbon and 92.2% chlorine. The molecular mass of the compound is 154 g/mole. Write the name for the compound.

3. What is a covalent bond? A covalent bond forms between two atoms that are sharing one or more pair of electrons. Usually occurs when the electronegativity difference between the two elements is small (<1.7) Covalent bonds form between two nonmetals. The bond results from an overlapping of orbitals. A covalent bond is a weaker bond than an ionic bond. Properties of compounds resulting from a covalent bond include: low melting point, gases or liquids at room temp (some are soft solids), do not conduct electricity, many are insoluble in water.

4. Naming covalently bonded compounds. The first element is named according to the element name. An –ide ending is added to the name of the second element. Numerical prefixes are used to indicate the number of each type of atom present.

5. Numerical Prefixes PrefixNumber *Mono (only used with the second element) 1 Di2 Tri3 Tetra4 Pent5 Hex6 Hept7 Oct8 Non9 Dec10

6. Name the following compounds CO2 CO N2O NO NO2 N2O3 N2O4 N2O5 PCl5 PCl3 SF6

7. Write the formulas for the following compounds: Sulfur trioxide Dioxygen difluoride Tetraphosphorus decaoxide Diboron trioxide Arsenic pentafluoride Silicon dioxide Monohydrogen dioxide Nitrogen trihydride

8. Types of Covalent Bonds A single covalent bond occurs when one pair of electrons (2 electrons) are shared between two atoms. A double covalent bond occurs when two atoms share two pairs (4 electrons) of electrons. A triple covalent bond occurs when two atoms share three pairs (6 electrons) of electrons.

9. Drawing Lewis Dot Structures Lewis dot structures can be drawn to represent the bonding that occurs within a covalent molecule. Atoms of hydrogen and halogens can only form one single bond each. (They only need to share 1 electron to form a complete octet). Lines represent the shared pairs of electrons or the chemical bonds between atoms. Unshared pairs are represented by dots or a line.

10. Example Draw the Lewis Dot Structure for CCl4

11. Example #2 Draw the Lewis dot structure for a molecule of NH3.

12. Example #3 Draw the Lewis dot structure for H2O.

13. For molecules involving atoms other than halogens or hydrogen Use the formula “N-A = S” to determine the number and type of bonds within the molecule. N represents the total number of valence electrons needed by all atoms to have a complete octet. A represents the total number of valence electrons available in all atoms within the molecule. S represents the total number of electrons that will need to be shared in order to form complete octets for each atom. Divide the number shared by 2 to determine the number of bonds that will form.

14. Draw the Lewis dot structure for O 2. N= 16 A=12 S=4 4/2=2 Therefore, 2 bonds are needed (or 4 electrons need to be shared) in order for this molecule to form.

15. Draw the Lewis dot structure for N 2. Step 1: Solve the equation “N-A = S” Step 2: Divide “S” by 2. Step 3: Draw the general structure of the molecule Step 4: Fill in the bonds. Step 5: Fill in the remaining valence electrons so that all atoms have a stable arrangement (8 electrons)

16. Draw the Lewis dot structure for CO 2 Step 1: 24 – 16 = 8 Step 2: 8/2= 4 Step 3:

17. Draw the Lewis dot structure for HCN Step 1: 18-10 = 8 Step 2: 8/4 = 2 Step 3:

18. Homework: Name and Draw Lewis Dot Structures for the following molecules: 1) PCl37) HCl 2) OF28) CS2 3) N29) H2CO 4) Br210) C2H2 5) O2 6) SiF4

19. Polar vs Nonpolar Bonds If the electrons are shared equally, it is called a nonpolar covalent bond. (This type of bond only occurs if the electrons are shared between identical atoms) If the electrons are shared unequally, it is called a polar covalent bond.

20. Polar and Nonpolar Molecules Molecules can also be polar and nonpolar. Molecules are nonpolar if: 1) the bonds are nonpolar 2) the polar bonds are arranged symmetrically Molecules are polar if the polar bonds are arranged asymmetrically.

21. Lewis Dot Diagrams Cl2 Linear Nonpolar bonds Nonpolar molecule Chlorine

22. Lewis Dot Diagrams H2O Bent Polar bonds Polar molecule Dihydrogen monoxide

23. Lewis Dot Diagrams NH3 Trigonal pyramidal Polar bonds Polar molecule Nitrogen trihydride

24. Lewis Dot Diagrams CH4 Tetrahedral Polar bonds Nonpolar molecule Carbon tetrahydride

25. In covalent compounds, atoms become stable by ___ their valence electrons. 1. transferring 2. sharing

26. A ___ covalent bond is the result of an equal share of electrons by both atoms. 1. polar 2. nonpolar

27. A cation has a ___ charge. 1. positive 2. negative

28. When an atom ___ electrons, it becomes positively charged. 1. gains 2. loses

29. In the formula CO 2, the number 2 is called a ___. 1. superscript 2. oxidation number 3. charge 4. subscript

30. What is the correct name for PCl 3 ? 1. Monophosphorus trichloride 2. Phosphorus chloride 3. Phosphorus trichloride 4. Traphosphorus chloride

31. What is the correct name for Li 2 O? 1. Lithium oxide 2. Dilithium oxide 3. Lithium (II) oxide 4. Lithium dioxide

32. Which is not a diatomic molecule? 1. Fluorine 2. Nitrogen 3. Bromine 4. Boron

33. Which element is a nonmetal? 1. Boron 2. Lithium 3. Carbon 4. Magnesium

34. Which element has 7 valence electrons? 1. Boron 2. Nitrogen 3. Fluorine 4. Manganese

35. Noble gases are stable because they have __ valence electrons. 1. 2 2. 4 3. 6 4. 8

36. The noble gases are in which block of the periodic table? 1. s 2. p 3. d 4. f

37. Electrons have what charge? 1. -1 2. +1 3. 0

38. How many valence electrons are in an atom of oxygen? 1. 2 2. 4 3. 6 4. 8

39. How many shared pairs are present? 1. 1 2. 2 3. 3 4. 4

40. How many electrons are not shared? 1. 1 2. 2 3. 3 4. 4

41. How many single bonds are present? 1. 1 2. 2 3. 3 4. 4

42. Are the bonds polar or nonpolar? 1. Polar 2. Nonpolar

43. What is the shape of the molecule? 1. Linear 2. Bent 3. Trigonal pyramidal 4. Tetrahedral

44. Is the molecule polar or nonpolar? 1. Polar 2. Nonpolar

45. 10 ml of the substance has a mass of 9 g. What is its density? 1. 0.9 g/ml 2. 1.0 g/ml 3. 1.1 g/ml 4. 19 g/ml

46. What is the percent oxygen in the substance? 1. 11% 2. 33% 3. 67% 4. 89%

47. Double and Triple Bonds A double covalent bond occurs when two atoms share two pairs (4 electrons) of electrons. A triple covalent bond occurs when two atoms share three pairs (6 electrons) of electrons.

48. Examples of compounds consisting of double bonds. CO2 O2 C2H4

49. Examples of compounds consisting of triple bonds. N2 HCN C2H2