Nuclear Chemistry

Aim: What is radioactivity and how do nuclear reactions differ from chemical

reactions?

Learning Objectives:1.Students should understand what causes an isotope to be radioactive, which elements are radioactive and that the process of radioactivity changes the element.

2.Students should be able to recognize the symbols of radiation particles.

3.Students should be able to distinguish nuclear reactions from other reactions and be able to identify the type of nuclear reaction.

4.Students should be able to determine the missing particle in an incomplete nuclear reaction.

Introduction1. The ratio of protons to neutrons determines the stability of an isotope. 1:1 ratio = stable. 2. All elements above 83 are unstable and thus all of their isotopes are radioactive.3. Nearly every element below 83 has at least one radioactive isotope (called radioisotope).4. Radioactive isotopes “decay” (change) into other elements by losing particles and energy.5. When particles are lost from the nucleus it results in one element becoming another. This is called transmutation.

Which isotope is radioactive?

The three isotopes of hydrogen.

Note the nucleons.

Some Common Forms of RadiationMissing information can be found on Table O of the

Reference Tables.Particle Mass Charge Notation and

SymbolPenetrating Power

Alpha Low, cannot pass through paper

Beta Moderate, cannot pass though skin

Positron Moderate, cannot pass through skin

Gamma High, can pass into body, blocked by lead

Which particle is which?

NotationAtomic# Mass Neutrons

TYPES OF NUCLEAR

REACTIONS

Natural Transmutation(Look for only one reactant)

Alpha Decay: alpha particle in the products

Beta Decay: beta particle in the products

Positron Emission: positron in the products

Alpha DecayNatural Transmutation (Spontaneous)

Beta DecayNatural Transmutation (Spontaneous)

Positron Emission Natural Transmutation (Spontaneous)

HW: Pages 219-220 Q 1-15

Artificial Transmutation

An alpha particle, neutron or proton is combined with an atom

to make a heavier atom.

Artificial Transmutation

• Distinguish artificial transmutation from natural transmutation by looking for alpha particles, protons or neutrons on the reactant side.

• The bombarding particle (alpha, beta or neutron) combines with the nucleus and makes one heavier atom.

Fission

Used in nuclear bombs, a heavy nucleus is split by being bombarded

with a neutron.

Fission• Splitting of a heavy nucleus to produce lighter nuclei.• Distinguish from artificial transmutation by looking for

multiple atoms on the product side.

Fusion

Occurs on the sun, hydrogen atoms fuse to form helium atoms.

Fusion• Combining light nuclei to make heavier nuclei.

http://antwrp.gsfc.nasa.gov/apod/ap051106.html

E=mc2

• Fission and fusion both result in some loss of matter. Meaning the mass of the products is slightly less than the mass of the reactants. What law is being broken? How is that possible?

• Why might fusion reactions be a better energy source that fission reactions?

Identify the following reactions

Applying Conservation of Mass and Charge to find the missing particle.

HW: Page 221 Q 16-23Page 223 Q 24-33

Aim: What can we learn from radioactive elements?

Learning Objectives:1.Students should be able to calculate the fraction of a radioactive sample remaining by using the isotopes’ half-life value.

2.Students should be able to determine the mass of a remaining radioactive sample by using half-life.

3.Students should be able to determine the mass of the original radioactive sample by using half-life.

4.Students should be able to determine half-life from a graph.

5.Students should know the uses of specific radioisotopes and the dangers/drawbacks of using radiation.

Half-LifeTable N

• Definition: The amount of time it takes for half of a sample of a radioactive substance to decay.

What is the half-life of this element?

Using Table N to Determine Radioactive Decay

Question Types:1.What fraction of a sample remains? Which isotope on Table N will have only 1/16 of it’s original mass after 28.8 seconds?2. How much mass remains? How much of an 80 gram sample of Radium-226 will be remaining after 8,000 years?3.What was the mass of the original sample? If 3.0 grams of Sr-90 in a rock sample remained in 1999, approximately how many grams of Sr-90 were present in original rock samples of 1943?

Applications

• Medicine: radiolabeling (short half-lives)

• Energy: nuclear reactor

• History/Science: radio dating (i.e. carbon dating, uranium dating) (longer half-lives)

HW: Read Pages 226-228, Uses and Dangers of Radioisotopes and answer questions on posted worksheet.

HW: Pages 225-226 Q 34-47Page 228 Q 48-57

CHAPTER QUESTIONSPages 229-232 Q 1-53

Practice