Chemical Bonding

1
Chemical Bonding

• Chapter 6

2
Covalent Compounds

• Nonmetal bonding with another nonmetal
• Electronegativity difference less than 1.7
• Electrons being shared

3
Draw the MO diagram for Chlorine and Hydrogen
4
Diatomic Molecules

• You must memorize these!!
• H2 N2 O2 F2 Cl2 Br2 I2
  (At2)
• Magnificent 7
• I wont hold you responsible for astatine, just
  know that trends in a group apply!

5
Formation of Covalent Bond
6
Bond stability
7
Octet Rule

• Noble gases have filled valence shells
• 2 (He) or 8 e-
• Octet Rule tells us that chemical compounds tend
  to form so that atoms obtain an octet of e- in
  its highest energy level.
• Visual Concepts

8
Exceptions

• Boron trifluoride BF3
• PF5 and SF6 can expand the shell and share more
  electrons. (10 and 12 respectively)

9
Electron Dot Notation

• Dots are used to represent valence electrons
  around an atom.
• Visual Concepts

10
Lewis Structure Rules

1. Add up total number of valence e-
2. Pick central atom and create the bonds
3. Surround the adjacent atoms.
4. Put extra electrons on the central atom.
5. Beg, borrow or steal so that all the atoms are
   stable (have a complete octet).
6. Make sure the number of valence e- you started
   with are the number you used!

11
Lets do

• CH4
• SiF4
• NCl3

12
Forming Multiple Bonds

• CO2
• N2O

13
Warm Up

• Draw the Lewis Structure for CS2
• Circle each atom showing a complete octet.

14
Exceptions

• Boron trifluoride BF3
• PF5 and SF6 can expand the shell and share more
  electrons. (10 and 12 respectively)

15
Lets talk about your WS

• Remind me to talk about the polyatomic ions!!
• Lets add some Dipoles!

16
Polyatomic ions

• Examples

17
Naming Covalent Compounds

• Covalent compounds are molecules or molecular
  compounds
• Indicate the number of each atom using
  prefixes..
• change the end of the name to ide

18
Covalent Prefixes

• Use the prefixes!
• 1- mono 6- hexa
• 2- di 7- hepta
• 3- tri 8- octa
• 4- tetra 9- nona
• 5- penta 10- deca
• Examples NO
• SiCl4

19
Practice

• Formulas to names

1. SO3
2. ICl3
3. PBr5
4. CO
5. CO2

• Names to formulas

• 1. Carbon tetrachloride
• 2. Dinitrogen monoxide
• 3. Dinitrogen tetroxide
• 4. Phosphorus triiodide
• 5. Sulfur heptafluoride

20
Homework

• Name all the molecular compounds on the Lewis
  Structure WS.
• Remember to get your ions names from the
  polyatomic ion sheet!

21
Multiple Covalent Bonds

• Bond length and strength
• Triple bonds are the shortest (pm) and have the
  most Energy (kJ/mol)
• Single bonds are the longest (pm) and have the
  least amount of Energy (kJ/mol)

22
Sigma s and Pi p bonds

• Sigma (s) bonds are single bonds
• Pi (p) bonds are the bonds that follow in a
  multiple bond situation

23
Resonance Structures

• Some molecules cannot be correctly identified by
  a single Lewis structure
• When you can draw two mirror images, you probably
  have a resonance structure
• For example Ozone O3
• Visual Concepts

24
Draw the Resonance Structures for

• Silicon Trioxide

25
Ionic vs covalent

• Visual Concepts

26
Properties of Covalent Compounds

• low melting point
• low boiling point
• many are gas and liquid at room temp
• typically do not conduct electricity when
  dissolved in water
• This is due to the fact that forces of attraction
  between molecules are much weaker when the
  electrons are being shared.

27
Conductivity Demo
28
Types of Bonds Lab

• Pre-lab- 8 minutes
• 1. Make a list of the characteristics of ionic
  and covalent compounds.
• 2. Discuss what makes the compounds different.

29

• Purpose- To classify 3 unknown samples as being
  either ionic of molecular using the known
  characteristics.
• Procedure Design an experiment that would help
  you identify if an unknown sample is ionic or
  covalent.
• Would it be helpful to test your known compounds
• and compare results?
• t

30
Materials Available

• Equipment
• Bunsen Burner
• Ring Stand
• Wire holder
• Test tubes
• Test tube racks
• Conductivity meter

• Chemicals
• Distilled water
• Sodium Chloride
• Sugar (C6H12O6)
• Unknown 1
• Unknown 2
• Unknown 3

31
Warm Up

• Determine if the following are ionic or covalent
  name them correctly.
• CF4
• NaCl
• CoF2
• SO2
• Would they be considered molecules or formula
  units?

32
Naming Acids

• Acids are molecular compounds that have hydrogen
  atoms
• Binary Acids- have 2 elements
• HCl- Hydrochloric Acid
• Oxyacids- Acids containing H,O, and a
  Nonmetal. (Polyatomic ion)

33
Oxyacids-

• Acids containing H,O, and a Nonmetal.
  (Polyatomic ion)
• If the poly ends in ate-
• change the end to ic and add acid
• H3PO4
• If the poly ends in ite-
• change the end to ous and add acid
• HNO2

34
Metallic Bonding
d-orbital electrons

• This is an extremely strong bond
• Gives metal luster, malleability, ductility,
  conduct electricity and heat

35
Metals

• Share a sea of electrons
• Explains why so many of them are good conductors
  of electricity.

36
Alloys

• Combination of metals
• Bronze copper and tin
• Brass zinc and copper
• Coin metal copper and nickel
• Solder lead and tin

37
Substitutional Alloy

• Some of the main metal atoms are replaced by
  other metal atoms of similar size. An example is
  brass where one-third of the atoms of the host
  copper are replaced with zinc atoms.

38
Interstitial Alloy

• Formed when some of the holes in the closest
  packed metal structure are occupied by small
  atoms.
• Steel is an interstitial alloy, containing carbon
  atoms in the holes of an iron crystal.

39

• Stainless steel is a substitutional/interstitial
  alloy