Nuclear Chemistry

Chapter 16 Tech Prep

Chapter 25 College Prep

Chapter 18 Honors

Key Terms

• Protons • Neutrons• Quarks• Nucleons *• Atomic Number• Mass Number• Isotopes• Nuclide **(honors only)

• Thermodynamic Stability*

• Kinetic Stability *• Radioactive Decay• Alpha Particles • Beta Particles• Gamma Particles• Zone of Stability *

Indicator C-2.5Compare alpha, beta, and gamma radiation in

terms of mass, charge, penetrating power, and the release of these particles from the nucleus.

• Radioactive nuclei that undergo decomposition falls into two categories: – change in mass number of the decaying nucleus – and those that do not change the mass number.

Alpha Radiation

• Mass number changes

• helium nuclei from a radioactive source; 2 protons and 2 neutrons; double positive charge.

• Common for heavy nuclides

• α-particle, __He

• 2 α-particle producers: U-238 and Th-230

Beta Radiation

• Mass number remains constant

• β particles (electron) , __e

• fast moving electrons formed from the decomposition of a neutron, negative charge.

• Th-234 and I-131 are beta producers.

• Neutron changes to a proton.

Gamma Radiation

• γ high-energy electromagnetic radiation given off by a radioisotope, no charge, no mass.

• Frequently accompanies nuclear decays and particle reactions

• Example: α-particle of U-238 (see page 880).

Penetrating Power

• Alpha

• Beta

• Gamma

Penetrating Power

• Alpha

• Beta

• Gamma

Low (0.05 mm) body tissue;

shielding – paper, clothing

Moderate (4mm) body tissue;

Shielding – metal foil

Very high – penetrates body easily; shielding – lead, concrete

(incomplete)

Indicator C-2.4

• Compare the nuclear reactions of fission and fusion to chemical reactions (including the parts of the atom involved and the relative amounts of energy released).

• What is fission and fusion?

Fission

• splitting of nuclei of certain isotopes into smaller fragments with similar mass numbers. Ex. U-235 and Pu-239

• Fission is used in nuclear reactor to produce energy.• It has to be controlled in the reactor. Controlling the

reaction involves 2 steps:• 1. Neutron moderation – reduces the speed of

neutrons.• 2. Neutron absorption – decreases the # of slow

moving neutrons.

Fusion

• (thermonuclear rxn.) – combining nuclei to produce a more stable nucleus of greater mass.

• Solar fusion hydrogen (protons) nuclei fuse to make helium nuclei.

• Nuclear Fusion occurs at extremely high temperature.

EQ - How does the nuclear reactions of fission and fusion compare to chemical reactions (including the parts of the atom involved and the relative amounts of energy released)?

• What parts are involved for nuclear rxns?

• What parts are involved in chemical rxns?• How does the energy released compare

between the two reactions? Hint: p. 897(honors)

C-2.6 Explain the concept of half-life, its use in determining the age of materials, and its significance to nuclear waste disposal.

What is half-life and why is it important?

Answer

• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.

Answer

• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.

• Carbon dating is important for determining the age of materials. All living things contain C-12 and C-14 in fixed ratios. The ratio changes when an organism dies, thus the C-14 decays to N -14. The ratio changes.

Answer

• Half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products.

• Carbon dating is important for determining the age of materials. All living things contain C-12 and C-14 in fixed ratios. The ratio changes when on organism dies, thus the C-14 decays to N -14. The ratio changes.

• Chemical waste may be hazardous. However, nuclear waste is even more hazardous because of the time-frame and the radiation. Only time can make nuclear waste not radioactive

Calculating amount of material remaining using half-life:

A = A0 x (1/2)n A0 = 1.0 g, n=4 [10.4/2.6=4]

A = 1.0 g x (1/2)4 A = 1.0 g x 1/16 = 0.063 g

Where

A0 is initial weight A is final weight (amount)

n is the number of half-lives. {n= Time passed ÷ half life}

• Refer to figure 18.3 (page 885).

Logical Method

n (half-life) Time Passed Amount

0 0 A0 =

BW: Half-life Problems

• #1 A patient is administered 40.0 mg of iodine-131 to assess the thyroid. How much of this nuclide will remain in the body after 40 days if the half-life is of iodine-131 is 8 days?

• #2 A patient is administered 100. mg of xenon-133 to assess the lungs. How much of this nuclide will remain in the body after 21.2 days if the half-life is of xenon-133 is 5.3 days?

Answers

• #1. A = A0 x (1/2)n n = 40/8 = 5 half-lives

A= 40.0 mg x (1/2)5 = 40.0 mg x (1/32) = 1.25 mg

• #2.A = 100. mg x (1/2) 4 n = 21.2/5.3 = 4 half-lives

A = 100. mg x (1/16) = 6.25 mg

Indicator C-2.8

Analyze a decay series chart to determine the products of successive nuclear reactions and write nuclear equations for disintegration of specified nuclides.

Refer to Table 18.3on page 886The Half-lives of Nuclides in the U-238 Decay Series.

• Answer the following questions.

• What nuclides have the following half-life?

a.) 5.0 days b.) 2.48 x 105 years

c.) 3.1 minutes d.) 1.62 x 103 years

• What is the particle produced from the above nuclides?

Answers

• What nuclides have the following half-life?

a.) bismuth-210 b.) uranium-234

c.) polonium-218 d.) radium-226

• What is the particle produced from the above nuclides?a.) beta b.) alpha

c.) alpha d.) alpha

Write the nuclear equations for disintegration of specified nuclides.

• U-238

• Ra-226

• Pb-214

• See page 880, Table 18.2 for more equations.

Detecting Radiation: Radiation emitted from isotopes and x-rays are forms of ionization radiation. It has enough energy to knock electrons off of some atoms. It cannot be detected by one’s senses.

• 3 devices used to measure the ionization radiation:

• Geiger counter - beta radiation

• Scintillation counter – all types

• Film badges – all types.

• Uses of Radiation:

• 1. Art

• 2. Crime labs

• 3. Agriculture

• 4. Diagnosing diseases

• 5. Treating diseases