Featured ACTIVITY: Two’s Company

Featured ACTIVITY

190

Two’s Company

Purpose

To use three-dimensional models to visualize small molecules.

Materials

  • gumdrops, marshmallows, and toothpicks

  • ruler

  • ball-and-stick molecular model set

image
Ken Karp Photography

Part 1: Gumdrop Molecules

  1. Create a methane molecule using gumdrops, marshmallows, and toothpicks.

  2. Make sure every pair of electrons in the molecule is as far away as possible from every other pair of electrons. Use a ruler to check the distances.

  3. Draw Lewis dot structures for the following molecules:

    1. CH4

    2. NH3

    3. H2O

  4. How many pairs of electrons are located around the central atom of each molecule?

  5. Besides the identity of the central atom, what is different about these three molecules?

  6. Using gumdrops and toothpicks, create ball-and-stick models of NH3 and H2O.

  7. Did you remember to include lone pairs? Fix your models if you have to so that lone pairs are represented. Do the lone pairs affect the shape of the molecule?

  8. Compare your three gumdrop models. Describe any similarities.

image
Ken Karp Photography

Part 2: Ball-and-Stick Models

  1. Use the molecular model sets to create models of CH4, NH3, H2O, and HF. Use black for carbon, white for hydrogen, red for oxygen, and blue for nitrogen.

  2. Add the appropriate lone pair paddles to your models.

  3. How many lone pair paddles would you need for an atom of neon? Explain your answer.

  4. Draw sketches of your three-dimensional models. What is the shape of each molecule if you ignore the lone pair paddles?

  5. Making Sense Explain how the lone pairs affect the shapes of these molecules.