CHEMISTRY 1

UNIT 8, ELECTRON DOTS AND VSEPR THEORY

Unit 8Guiding Questions:

  1. What are some ways to represent how elements combine to make compounds?
  2. How do we use Lewis Dot structures to represent chemical bonds?
  3. How does the VSEPR theory relate to intermolecular forces of attraction?
  4. What is hydrogen bonding and what is the most common example of it?
  5. What is the difference between intramolecular and intermolecular forces of attraction?

Key Vocabulary Terms (Mostly chapter 9 in text):

Aqueous solutionsolutesolvent

VSEPR theoryLondon Dispersion Forcespolarity

Hybridizationdipole-dipole interactionhydrogen bonding

van der Waals ForcesLewis Electron Dot Structures

  1. What is the difference between metallic, ionic, and covalent bonding?
  1. On what two things does the strength of an ionic bond depend?
  1. What are some examples of covalent bonds innature?
  1. How is electronegativity used to determine the kind of bond between two atoms?

Atom / Number of Valence Electrons / Number of Electrons Needed to Fill Valence Shell / Bonding Capacity
Carbon
Nitrogen
Oxygen
Halogens
Hydrogen
  1. Based on trends in electronegativity, which of the following substances show the most evendistribution of valence electrons? Explain your choice.

Ammonia (NH3)

Silver sulfide (Ag2S)

Phosphorus pentachloride (PCl5)

  1. Draw the Lewis dot structures for the following neutral atoms.
  2. Sodium b. phosphorus c. krypton d. aluminum
  1. What are the steps for drawing Lewis Dot structures? (See Handout)
  1. Create Lewis dot diagrams for the following molecules:
  2. hydrogen sulfide b. nitrogen trichloride c. carbon dioxide
  1. Draw structural formulas (using lines to show bonded electron pairs) for the compoundsbelow.
  2. Hydrogen sulfide b. nitrogen trichloride c. carbon dioxide
  1. Which molecules in questions 9 and 10 include double bonds? How many pair of electrons areshared in a double bond?
  1. How many pair of electrons are shared in a triple bond?
  1. List the 7 diatomic molecular elements, also known as the stupendous seven and give their electron dot structures.
  1. What do the letters VSEPR stand for? What is the basic assumption ofthis theory?
  1. Draw the Lewis dot diagram for a water molecule. Draw (as well as you can) the threedimensionalshape of a water molecule. How does the angle between the bonded hydrogens differ between the two representations?
  1. Why is the bond angle in a trigonal pyramidal molecule different from that in a tetrahedralmolecule?
  1. Complete the following table. Use the diagrams below the table to identify the answers for the final column.

Formula / Dot structure of
central atom / Number of bonding electrons / Number of nonbonding electron pairs / Name of Shape / Diagram of shape from below
SbH3
Cl2O
BeH2
SiF4

  1. List the kinds of intramolecular and intermolecular forces of attraction from strongest toweakest.
  1. What is a van der Waals force? Is it an example of a chemical bond? Why or why not?
  1. For different substances of similar molar mass, which type of intermolecular force is weakest? Give an example of a molecule that would exhibit this force.
  1. What makes a molecule polar?
  1. Give two examples of polar molecules that contain polar bonds. Give two examples of nonpolar molecules that contain polar bonds.
  1. What is a temporary dipole? What types of molecules are capable of having temporary dipoles? What is the name of the van der Waals force that involves temporary dipoles?
  1. Why type of intermolecular forces of attraction would be exhibited by each of the following substances?
  2. PF3
  1. N2
  1. HF
  1. BeH2
  1. What is hydrogen bonding? Give an example of a substance that would exhibit hydrogen bonding.
  1. The following substances have roughly the same molar mass. Which one is most likely to have the higher boiling point: H2S, F2, or CO2? Explain your choice.