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How to Construct a Trigonal Planar Molecule in 3-D

The electrons of atoms in a molecule can be like strangers in an elevator: they want to be as far from each other as conditions allow. Molecules also have different configurations, or molecular geometries, depending on how many atoms make up each molecule and how the atoms bond to each other. One of the simplest configurations is trigonal-planar geometry. A trigonal-planar molecule has a single central atom and three surrounding atoms. All the atoms of the molecule are on the same plane; also, the three surrounding atoms are separated by 120-degree angles.

Things You'll Need

1 piece of printer paper
Ruler
Protractor
Modeling clay in two different colors
3 craft sticks or toothpicks

Instructions

- 1
  Place a sheet of printer paper on the table in front of you. Make a dot in the middle of the sheet of paper with a pencil.
- 2
  Draw a straight line on the sheet of paper beginning at the dot in the middle of the paper and extending approximately 4 inches to your left using a ruler and the pencil.
- 3
  Place a protractor on the sheet of paper with its curve toward the top of the piece of paper so you can see the dot on the piece of paper through the small hole at the center of the straight bottom rule of the protractor. Align the protractor so its straight bottom rule covers the line you have drawn and the dot is still visible through the protractor's hole.
- 4
  Make a mark on the sheet of paper where you see "120" on the outside curved rule of the protractor. Remove the protractor and draw a straight line on the sheet of paper connecting the dot in the middle of the paper and the mark you have just made using your ruler and pencil.
- 5
  Place the protractor on the sheet of paper again so you can see the dot you have made through the small hole at the center of the straight bottom rule of the protractor and the curve of the protractor is on your right. Align the protractor so its straight bottom rule covers the line you have just drawn and the dot is still visible through the protractor's hole.
- 6
  Make another mark on the sheet of paper where you see "120" on the outside curved rule of the protractor. Remove the protractor and draw a straight line on the sheet of paper connecting the dot in the middle of the paper and the mark you just made using your ruler and pencil. You now have a dot in the middle of your piece of paper and three lines extending outward from that dot. An angle of 120 degrees separates each line from the line next to it.
- 7
  Shape modeling clay into a ball approximately the size of a walnut and place it on top of the dot in the middle of the piece of paper. This represents the central atom of your trigonal-planar molecule. Insert a craft stick or toothpick into the clay ball using one of the three lines you have drawn as a guide. Each stick or toothpick should be parallel to the table top and aligned with the line drawn on the piece of paper under it. Each stick represents a pair of electrons shared between the central atom and the three atoms that will surround it.
- 8
  Shape modeling clay of a different color into three small balls approximately the size of large marbles. These clay balls represent the three atoms that surround the central atom of the trigonal-planar molecule. Push one small ball onto the end of each stick or toothpick without disturbing the orientation of the stick to complete your trigonal-planar molecule model in three dimensions (3-D).

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