Isotopes, a Lab on Paper with Bags

Names:

Period:

Isotopes, a Lab on Paper with Bags

Essential Question:

Are all atoms of a single element the same? If not, what about those atoms is the same and what is different?

Background:

All the atoms of a single element have the same number of protons in the nucleus and the same number of electrons in the surrounding cloud. The atoms of a single element can have different numbers of neutrons. Because the protons and neutrons make up the mass of the atom, different atoms of the same element can have different masses.Atoms with the same number of protons but different numbers of neutrons are called isotopes. For example, hydrogen-1 has one proton and no neutrons, hydrogen-2 has one proton and one neutron, and hydrogen-3 has one proton and two neutrons. H-1, H-2, and H-3 are isotopes. (You may recall that H-3 is unstable.)

Procedure

1. There are 21 numbered bags that will be distributed around the room. Each bag represents one isotope of an atom. In each bag there will be a predetermined assortment of red, white, and black beans (representing the protons, neutrons, and electrons in an atom).

2. Count the number of protons (red beans), neutrons (white beans) and electrons (black beans) in each baggie and enter the data in the table below. DO NOT OPEN THE BAG.

3. a. Use your periodic table to identify the element.

b. From the periodic table you can find the average atomic mass for that element.

c. The mass number is the sum of the number of protons and neutrons.

d. The isotope names are written as the element followed by the mass number, carbon-12 oroxygen-16 as examples.

4. Once you complete the table, complete the questions below the table, and once all questions are complete, turn in the activity.

Data and Analysis:

Bag / number
protons / number
electrons / number
neutrons / average
atomic
mass
(from PT) / mass
number / atomic
number / element
symbol / isotope
name
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

Analysis:

1. How many different elements did you work with today?

2. How many hydrogen isotopes did you find?

3. How are they the same?

4. How are they different?

5. Based on your answers to questions 3 and 4, what is a reasonable definition for “isotopes”?

6. Does the number of electrons affect the mass of the isotopes?

Why or why not?

7. How many neutrons does oxygen-17 have?

8. What is the correct nuclear symbol for nitrogen-14?

9. What does the 35 in the name chlorine-35 represent?

10. Cobalt-60 is used in radiation therapy for cancer. How many neutrons does an atom of cobalt-60 have?

11. Iodine-131 is an isotope used to detect thyroid problems. How is iodine-131 the same as iodine-126?

12. How is iodine-131 different from iodine-126?