Chapter 6 Covalent Bonds

1
Chapter 6 Covalent Bonds Molecular Forces

• Mr. Kupfer
• Chem. I
• 2004 - 2005

2
Ionic Bonds

• Give away
• Always neutral

3
Covalent Bonds

• Sharing
• Non-Polar
• Share e-s equally
• Polar
• Share e-s unequally

4
Electronegativity
5
Polar Molecules

• Two Ends

6
Homework

• P. 201 4, 6, 8
• 4) Moving to the right it gets bigger. Moving
  down it gets smaller.
• 6)a) Cs Br -- .8 3.0 2.2 (Ionic)
• b) H S -- 2.2 2.6 .4 (Non Polar)
• c) Ca O -- 1.0 3.4 2.4 (Ionic)
• d) Si Cl -- 1.9 3.2 1.3 (Polar)
• e) As P -- 2.2 2.2 0 (Non Polar)
• f) Se Br -- 2.5 3.0 .5 (Polar)

7
Homework

• 8) H O -- 2.2 3.4 1.2 (Polar)

8
Review Quiz

• What type of bond is not sharing?
• A) Covalent
• B) Molecular
• C) Ionic
• Do Polar Bears share equally?
• A) Yes
• B) No
• C) What?

9
Review Quiz

• T or F Polar covalent bonds share e-s unevenly.
• A) True
• B) False
• C) Both
• T or F Non-Polar covalent bonds share e-s
  unevenly.
• A) True
• B) False
• C) Both

10
Review Quiz

• Electronegativity is
• A) How negative something is
• B) Tendency to attract extra e-
• C) Ability to remove an e- from an atom
• A valence e- is
• A) An outer shell e-
• B) An electron that wears a vail
• C) A supercharged e-

11
Lewis Electron-Dot Structures

• e-s are involved in bonding
• Specifically, the outer shell, or valence, e-s
  are involved in the bonding.
• Gilbert Newton Lewis developed a method to
  represent bonding in e-s.

12
Lewis Electron-Dot Structures

• 2 parts
• Chemical Symbol
• Valence e-

13
Lewis Electron-Dot Structures
Li
1s22s1
Li
Be
1s22s2
Be
C
1s22s22p2
O
1s22s22p4
Ne
1s22s22p6
14
Covalent Dots

• Lewis Dot Structures can represent covalent bonds.

?
Tough luck buddy, I cant just give you mine!
Why dont we share!
Whats wrong?
Okay, we can try
Well, its probably stupid. Eat poop!
I need an electron. I dont know what to do!
Thats odd, I also need an electron too.
I have an IDEA!
This is Emily Chlorine.
This is Marcy Chlorine.
15
Covalent Dots

• The two e-s in the middle are shared.
• Where two atoms touch, the e-s are shared.
• It can also be drawn like this

16
Drawing Dot Structures

• Hydrogen and Halogen
• bind to only one other atom
• usually on the outside or end
• Lowest electronegativity is often the center
• Place one valence e- on each side before placing
  two

17
Example CH3I

• Determine total of valence e-
• 1 C with 4 1 x 4 4
• 3 H with 1 3 x 1 3
• 1 I with 7 1 x 7 7
• 14
• Arrange the atoms symbols to show how the atoms
  bond.
• Compare the of valence e-s
• Change dots to line
• Check octet rule

18
Work

• P. 205 1 2 in notes

19
Multiple Bonds

• Sometimes atoms will form multiple bonds.
• C, N, O tend to form multiple bonds
• H Halogens tend not to

20
Example CH2O

• Determine total of valence e-
• 1 C with 4 1 x 4 4
• 2 H with 1 3 x 1 2
• 1 O with 6 1 x 6 6
• 12
• Arrange the atoms symbols to show how the atoms
  bond.
• Compare the of valence e-s
• Change dots to line
• Check octet rule

21
Review Quiz

• A drawing with a chemical symbol surronded by
  dots is a(n)
• A) Electron Configuration
• B) Lewis Electron Dot Structure
• C) Circle Picture
• The dots represent
• A) Protons
• B) Neutrons
• C) Electrons

22
Review Quiz

• What group are B Al in?
• A) 12
• B) 13
• C) 14
• How many valence electrons do they have?
• A) 1
• B) 2
• C) 3

23
Review Quiz

• Which of the following is most likely to be on
  the outside of a dot structure?
• A) H
• B) O
• C) C
• Which is most likely to form multiple bonds?
• A) Cl
• B) Na
• C) C

24
Review

• Lewiss middle name was
• A) Newton
• B) Galileo
• C) Einstein

25
Review Quiz

• Which of the following is correct?
• A)
• B)
• C)

26
Valence Electrons

• Atoms have energy levels
• Energy levels have orbitals

27
Valence Electrons

• Level/ orbits
• 1
• 1s
• 2
• 1s
• 3p
• 3
• 1s
• 3p
• We dont deal with the rest! ?

28
Valence Electrons

• 1s22s2
• Be
• Outer energy level?
• 2
• Full?
• No
• Has 2, wants 8
• Solution?
• Remove 2 and make the outer level 1.
• It is full
• 1s22s2 2e- 1s2

29
Valence Electrons

• 1s22s22p3
• N
• Outer energy level?
• 2
• Full?
• No
• Has 5, wants 8
• Solution?
• Add 3 to fill the outer level
• 1s22s22p3 3e- 1s22s22p6

30
Molecular Shape
31
Review Quiz

• How many valence electrons does carbon have?
• A) 2
• B) 3
• C) 4
• What is the shape of H2?
• A) Trigonal Pyramid
• B) Linear
• C) Bent

32
Review Quiz

• What shape does H2O take?
• A) Tetrahedron
• B) Trigonal Pyramid
• C) Bent
• What is the shape of CH4?
• A) Trigonal Pyramid
• B) Linear
• C) Tetrahedral

33
Review Quiz

• Why do compounds take these peculiar shapes?
• A) So e-'s get closer together
• B) Because e-'s repel each other
• C) Because the e-'s orbits are not defined
• What does VSEPR stand for?
• A) valence shell electron pair repulsion
• B) valence skull energy pair reception
• C) very special energy pair reaction

34
Review Quiz

• How many valence electrons would an element with
  electron configuration 1s22s22p4 have?
• A) 2
• B) 4
• C) 6
• What element is this?
• A) O
• B) N
• C) F

35
Review Quiz

• How many valence electrons would an element with
  electron configuration 1s22s22p63s23p4 have?
• A) 2
• B) 4
• C) 6
• What element is this?
• A) P
• B) S
• C) Ci

36
Naming Covalent Compounds

• Use Latin prefixes for of atoms
• More electronegative atom 2nd, end in -ide

37
Naming Covalent Compounds

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

38
Naming Covalent Compounds

• P4O6
• Phosphorus
• Oxygen
• 4
• Tetra
• 6
• Hexa
• tetraphosphorus hexoxide

39
Naming Covalent Compounds

• Drop double vowels
• N2O4
• dinitrogen tetraoxide
• dinitrogen tetroxide
• P. 213 10 11
• 10 minutes

4
3
2
1
30
5
0
6
7
8
9
10
40
Polyatomic Ion Dot Structures

• How are ions different?
• Not neutral
• Extra or lacking e-'s
• Draw essentially the same, adjust ending valence
  e-'s.

41
Example NH4

• Determine total of valence e-
• 1 N with 5 1 x 5 5
• 4 H with 1 4 x 1 4
• 9
• Arrange the atoms symbols to show how the atoms
  bond.
• Compare the of valence e-s
• Change dots to line
• Add charge with brackets
• Check octet rule

42
Resonance Structures

• Some molecules are represented by more than one
  Lewis dot structure.
• SO2
• Can be written more than one way
• We know the bond lengths are equal
• Can draw either way
• Resonance Structure
• Like having 1.5 bonds

43
Practice

• Draw
• ClO3-
• SO42-
• CO32-

44
Homework

• SF4
• sulfur tetrafluoride
• BCl3
• boron trichloride
• PBr5
• phosphorus pentabromide
• N2O5
• dinitrogen pentoxide
• S2Cl2
• disulfur dichloride
• SO3
• sulfur trichloride

45
Homework

• CS2
• SF6
• N2O4
• ClF3

46
Homework

• carbon tetrafluoride
• xenon trioxide
• dihydrogen dioxide

47
Homework