Take Home Lab #3

Take Home Lab #3:  Probability of Finding an Electron

Question: What does it mean to say that an electron has a probability of being found in a certain location around the nucleus?

Safety: No safety concerns.

Materials: Pen or pencil, copy of target

Procedure: It is known that electrons do not actually fly around in fixed orbits like planets. When you see textbook drawings of electrons in orbits, the orbits only represent where it is the most probable that the electron may be found at any moment. Sometimes this is called the electron cloud. The electrons also do not form a cloud; that is just a model representing the likelihood that an electron will be found at a certain location. You will simulate this probability analysis by dropping a pen at a target and counting how many times the pen marks in each area.

1. Take the target paper and put it on the floor. While aiming for the center of the target, hold the pen at arm’s length, drop it 50 times, tip first, so that it will make a mark on the paper.

2. Count how many times the pen struck each of the areas on the target. (Enter this on the hits part of your data chart) If it is on the line, try to determine which side it is closer to hitting. Then count the total hits inside of that circle (for example, for circle 4, that would be all the hits in circle 1, 2, 3, and 4—Enter this in total hits on your data table).

3. Fill in the chart and graph your results with a smooth curve. Then calculate the probability using the equation (total hits/total drops) x 100. Make a bar graph showing the probability.

Data

Circle 1	Hits =	Total hits:	Area= 4.9 cm2	Probability = ___%
Circle 2	Hits =	Total hits:	Area= 14.7 cm2	Probability = ___%
Circle 3	Hits =	Total hits:	Area= 24.5 cm2	Probability = ___%
Circle 4	Hits =	Total hits:	Area= 34.4 cm2	Probability = ___%
Circle 5	Hits =	Total hits:	Area= 44.2 cm2	Probability = ___%
Circle 6	Hits =	Total hits:	Area= 53.0 cm2	Probability = ___%

      Probability

 

                                                Area

Wrap-Up

1. In which circle did the most hits occur?

2. Scientists consider the size of the 1s orbital to be the circle in which there is a 90% chance of finding the 1s electron. Which is the smallest circle that contains 90% of your dots (45 dots)?

3. If you dropped your pen one more time, could you assume that it will fall in the ring noted in #1?