Covalent Bonding

1. Covalent Bonding

2. Covalent Compounds A molecule is an uncharged group of two or more atoms held together by covalent bonds. Covalent compounds occur between two nonmetals or a nonmetal and hydrogen.

3. Covalent Compounds The attraction of two atoms for a shared pair of electrons is called a covalent bond. In a covalent bond, atoms share electrons and neither atom has an ionic charge.

4. Covalent Bonds Covalent bonds occur between 2 nonmetals because nonmetals hold onto their valence electrons. They can’t give away electrons to bond, yet, they still want noble gas configuration.

5. Covalent Bonds They get it by sharing valence electrons with each other. By sharing, both atoms get to count the electrons toward noble gas configuration.

6. Properties of Covalent Molecules Bond between atoms is strong, but bond between molecules is weak compared to ionic compounds Covalent molecules tend to have lower melting and boiling points softer solids many exist as gases at room temperature nonconductors

7. Properties of Covalent Molecules Exception: Network Covalent Solids have network structure similar to lattice hard, brittle examples- quartz and diamond

8. Covalent Bonding F Fluorine has seven valence electrons

9. Covalent Bonding F F A second fluorine atom also has seven valence electrons.

10. Covalent Bonding • Both end with full orbitals. F F

11. Single Covalent Bond • A sharing of two valence electrons. • Only nonmetals and hydrogen. • Form molecules. • Different from an ionic bond. • No transfer of electrons • Balanced attractive and repulsive force between nuclei and electron clouds • Neither atom has a charge

12. Single Covalent Bond Group 7A elements and hydrogen form single covalent bonds with each other as diatomic molecules H2 Cl2 I2 Br2 F2

13. Water H Each hydrogen has 1 valence electron. Each hydrogen wants 1 more.

14. Water O The oxygen has 6 valence electrons. The oxygen wants 2 more.

15. Water O H Hydrogen and oxygen share to make each other happy. The first hydrogen is happy, but the oxygen still wants one more electron.

16. Water O H H A second hydrogen attaches. Every atom has full energy levels.

17. Multiple Bonds Sometimes atoms share more than one pair of valence electrons. A double bond is when atoms share two pair (4 total) of electrons. A triple bond is when atoms share three pair (6 total) of electrons.

18. Multiple Bonds Triple bonds are stronger and shorter than double bonds. Double bonds are stronger and shorter than single bonds.

19. Multiple Covalent Bonds • Oxygen and nitrogen also occur as diatomic • molecules • Oxygen forms a double bond • Nitrogen forms a triple bond • O2 N2

20. Carbon Dioxide O C CO2- Carbon is central atom Carbon has 4 valence electrons Wants 4 more Oxygen has 6 valence electrons Wants 2 more

21. Carbon Dioxide O C Attaching 1 oxygen leaves the oxygen 1 electron short and the carbon 3 electrons short

22. O O Carbon Dioxide • Attaching the second oxygen leaves both oxygen 1 short and the carbon 2 short C

23. O O Carbon Dioxide • The only solution is to share more C

24. O O Carbon Dioxide C

25. O Carbon Dioxide O C

26. O Carbon Dioxide O C

27. O Carbon Dioxide O C

28. Carbon Dioxide O C O

29. Carbon Dioxide • Requires two double bonds • Each atom gets to count all the atoms in the bond O C O

30. Naming Covalent Compounds

31. Molecular Compounds • Molecular compounds are made of molecules. • They are made by joining nonmetal atoms together into molecules. • Prefixes are used to indicate the number of each atom

32. Prefixes • 1 mono- • 2 di- • 3 tri- • 4 tetra- • 5 penta- • 6 hexa- • 7 hepta- • 8 octa- • 9 nona- • 10 deca-

33. Prefixes • The name will consist of two words. Prefix name prefix name -ide • One exception: don’t write mono- if there is only one of the first element.

34. Prefixes • The following double vowels cannot be used when writing names: • (oa) • (oo)

35. Example • NO2 • There is one nitrogen • Drop “mono” • Nitrogen • There are two oxygens • dioxide • Nitrogen dioxide

36. Example • N2O • There are two nitrogens • dinitrogen • There is one oxygen • monooxygen

37. Example • N2O • monooxygen • You cannot run (oo) together, so • monoxygen

38. Example • N2O • monoxygen • You need the suffix -ide • monox ygen ide

39. Example • N2O • dinitrogen monoxide

40. Sample Problem • Name the following molecular compounds. • Cl2O7 dichlorineheptoxide • CBr4 carbon tetrabromide

41. Naming Molecular Compounds • You will not need to criss-cross oxidation numbers. • Molecular compound names tell you the number of atoms through the use of prefixes.

42. Example • diphosphorus pentoxide • The name implies there are 2 phosphorous atoms and 5 oxygens. P2O5

43. Example • sulfur hexaflouride • The name implies there is 1 sulfur atom and 6 fluorines. SF6

44. Problem • Write the formulas for the following molecules. • carbon tetrahydride CH4 PF3 • phosphorus trifluoride

45. Acids Naming and Writing Formulas

46. Acids • Acids are compounds that give off hydrogen ions (H+) when dissolved in water. • Acids will always contain one or more hydrogen ions next to an anion. • The anion determines the name of the acid.

47. Naming Binary Acids • Binary acids contain hydrogen and one anion whose name ends in–ide. • When naming the acid, put the prefix hydro- and change -ide to -ic acid.

48. Example • HCl • The acid contains the hydrogen ion and chloride ion. • Begin with the prefix hydro-, name the nonmetallic ion and change -ide to -ic acid. hydro chlor ide ic acid

49. Example • H2S • The acid contains the hydrogen ion and sulfide ion. • Begin with the prefix hydro- and name the nonmetallic ion. hydro sulf ide

50. Example • H2S • The next step is change -ide to -ic acid, but for sulfur the “ur” is added before -ic. hydro sulf ide ur ic acid