C. Comprehension Tasks

/. Write T before true statements and F before false statements. Do not look back at the reading. If the statement is false, correct it.

1. Isotopes of the same element have different numbers of protons.

2. A radioactive isotope decays or loses particles from its nucleus.

3. All elements have more that one isotope.

4. Radioactive isotopes are not very useful.

5. Protium, deuterium, and tritium are isotopes of hydrogen.

6. All elements are radioactive.

7. U-235 and U-238 are different elements.

8. Protons and neutrons are particles.

9. Stable isotopes decay or lose particles.

10. H-l, H-2, and H-3 are three isotopes of hydrogen.

2. Write the line number of the sentence or sentences that support your answer to question 10 .

D. Vocabulary Development

Match the definition taken from the text and the physical phenomenon.

a. An isotope b. U-235 c. A stable isotope d. A radioisotope

1. an isotope which is used for atomic bomb and nuclear reactors 2. atoms of the same element that have different atomic weight (or mass number) and different number of elec­trons 3. an isotope which loses or gives off particles from its nucleus 4. an isotope which does not decay or lose particles from its nucleus. 10

E. Outline

This article has three parts. Answer the questions to complete the outline/

1. What are two examples of elements that have isotopes?

2. What are two kinds of isotopes?

3. What are some uses of radioisotopes?

F. Additional Reading

1. The following text will deal with isotopic tracers. What do you know about them? Discuss it with another student.

1. Read the text to learn more about isotopic tracers.

Isotopic Tracers

Isotopic Tracer is an atom of an isotope used to observe the movement of certain materials in chemical, biological, or physical processes. The term tracer is applied commonly to any radioactive isotope employed in tracing the course of non-radioactive substances. In scientific usage, however, the term is applied also to less abundant non-radioactive, or stable, isotopes that are suitable for use in tracer techniques.

Tracers may be used to follow the movement of substances in large or small amounts as well as at molecular or atomic levels. The observations may be made by the measurement of radioactivity in the case of radioac­tive tracers, or of the relative abundance of isotopes in applications em­ploying stable isotopes as tracers. Instruments used to detect radiation include the electroscope, the scintillation counter, and the Geiger-Muller counter. In investigations using stable isotopes as tracers, the instrument most commonly employed is the mass spectrometer, a device that can determine the relative amounts of various isotopes in a sample ot the substance being analyzed. Tracers have important applications in many fields of scientific research and in medicine, agriculture, and industry.

3. Ask your partner some questions to check understanding.

4. Read the following sentences and try to define the field in which tracers are applied. If you know more about it exchange your knowledge

with another student.