Chemistry

Unit: Atomic Structure

Name: ______Date: ______MOD: ______

ELECTRON DISTRIBUTION USING PEAS

Purpose

Describe differences in the nucleus and the electron cloud in order to analyze the structure of the atom.

MATERIALS

goggles1 pieces of circular filter paper, 15-25 cm in diameter

1 metric rulers1 marking pens

1 pairs scissors1 tripod ring stands

1compasses1 sheets of butcher paper/art paper

1-lb bag of dried whole peas1 beakers, 150-ml

1 plastic cups (100 peas each)

PROCEDURE

CAUTION: Wear your goggles and lab apron at all times.
  1. Put on your goggles. Fold the filter paper in half and then fold it again into quarters. Using the ruler, measure up 1.5 cm from the closed point of the paper and make a mark. Make a small hole in the bottom of the folded filter paper by cutting at the 1.5 – cm mark with the scissors. Insert the cut filter paper into the ring of the tripod ring stand to create a funnel with the small hole at the bottom.
  1. Use the compass to draw a circle with a radius of 2 cm in the center of a large sheet of paper. Then draw four more concentric circles 2 cm apart, around the first circle. Number the rings 1-5, starting from the center.
  2. Mark the center of the innermost circle with a large dot. Let this dot represent the nucleus of the atom. Place the ring stand so that the hole in the filter paper is exactly above the large dot, or nucleus, as shown in Figure 1.
  1. Count out 100 dried peas and place them in a plastic cup. Pinch closed the hole at the base of the filter paper and add the 100 dried peas, or “electrons,” to the filter. Let go of the filter, allowing the peas to fall through the small hole onto the target beneath the ring stand. If the peas jam up in the filter, push them gently to keep them moving.
  2. Count the number of peas in each ring around the nucleus, as well as any that fall outside the rings. Record the data in the table, beginning with the innermost ring number 1.
  3. Gather up the peas and place them in the plastic cup. Return all equipment to the supply area. Clean up your work area and wash your hands before leaving the lab.

DATA

DATA TABLE: Distribution of Peas
Ring / Distance from Nucleus / Number of Peas in Ring
1 / 2 cm
2 / 4 cm
3 / 6 cm
4 / 8 cm
5 / 10 cm
Outside of rings / Beyond 10 cm

Using the data in the table, graph the number of peas vs. the distance from the nucleus (Bar Graph).

ANALYSIS AND CONCLUSIONS

  1. Judging from your graph, in which region would you be most likely to find electrons? In which region would you be least likely to find electrons?

______

  1. Were you able to determine the exact path by which each pea (electron) arrived at its position on the target? How does this finding relate to the quantum theory?

______

  1. Why do you think that many people persist in visualizing the atom according to the out-dated Bohr model as opposed to accepting the quantum-mechanical model?

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