Nuclear Chemistry MSTA 2010 Convention Michelle Robinson

Introduce yourself. What do you teach? 1. AP Chemistry & Chemistry 2. Chemistry 3. Physics and/or AP Physics 4. Physical Science 5. Other High School Science 6. Middle School Science 7. Other

How comfortable are you with the nuclear material? 1. Very Comfortable, just need ideas of activity 2. Took a nuclear course in college but need refresher. 3. Not my area of expertise at all. Haven’t really had any formal training on this material. 4. No clue. Please help

What is the difference between regular chemical reactions and nuclear reactions? 1. Nuclear reactions always cause explosions, chemical reactions don’t 2. Nuclear reactions only happen in the stars, chemical happen on earth 3. Nuclear reactions change atoms into other atoms, chemical reactions don’t 4. Nuclear reactions are dangerous, chemical - not so much

Chemistry Standards MS DOE 2010 Curriculum Write equations for nuclear decay reactions balance equations representing nuclear reactions Three major types of radioactive decay and the properties of the emissions The concept of half-life for a radioactive isotope based on the principle that decay is a random process 2d & 3a Describe how the nucleus changes during these reactions 2d-1 2d-4 2d-2 2d-3 Compare the resulting radiation with regard to penetrating ability.

Describe the three major types of radiation Short version TLW: Describe the difference between chemical and nuclear reactions Be able to write and balance nuclear reactions Define and calculate half life

1.Electrons react outside nucleus. 2.The same number of each kind of atom appear in the reactants and products. 3.Isotopes react the same. 4.Depend on chemical combination. 5.Energy changes equal kJ/mol. 6.Mass reactants = mass products. 1. Protons and neutrons react inside nucleus. 2. Elements transmute into other elements. 3. Isotopes react differently. 4. Independent of chemical combination. 5. Energy changes equal 10 8 kJ. 6. Mass changes are detectable. Reactions

Unstable nuclei decay naturally by emitting particles 3 most common types of radioactive decay Alpha Beta Gamma Natural decay

Occurs when nucleus is too large Alpha Particles U  U He

Occurs when the neutron to proton ratio is low. Beta Particle I Xe  + e 0−10−1

Gamma Particles

Other particles

A proton turns into a neutron and a positron and the positron is emitted. A positron is basically a positively charged electron Occurs when the neutron to proton ratio is too small Positron Emission

© 2009, Prentice-Hall, Inc. Electron Capture (K-Capture) Occurs when the neutron to proton ratio is low. Addition of an electron (from a nearby electron cloud) to a proton in the nucleus is known as electron capture or K-capture. The result of this process is that a proton is transformed into a neutron. p e 0−10−1  n 1010

Balancing Nuclear Reactions

Which particle fills the blank?

1. Sodium Sodium Aluminum Aluminum - 13

Stability of Nucleus video

© 2009, Prentice-Hall, Inc. Neutron-Proton Ratios Any element with more than one proton will have repulsions between the protons in the nucleus. A strong nuclear force helps keep the nucleus from flying apart.

© 2009, Prentice-Hall, Inc. Neutron-Proton Ratios Neutrons play a key role stabilizing the nucleus. Therefore, the ratio of neutrons to protons is an important factor.

© 2009, Prentice-Hall, Inc. Neutron-Proton Ratios For smaller nuclei (Z  20) stable nuclei have a neutron-to-proton ratio close to 1:1.

© 2009, Prentice-Hall, Inc. Neutron-Proton Ratios As nuclei get larger, it takes a greater number of neutrons to stabilize the nucleus.

© 2009, Prentice-Hall, Inc. Stable Nuclei The shaded region in the figure, the so- called belt of stability, shows what nuclides would be stable.

© 2009, Prentice-Hall, Inc. Stable Nuclei Nuclei above this belt have too many neutrons. They tend to decay by emitting beta particles.

© 2009, Prentice-Hall, Inc. Stable Nuclei Nuclei below the belt have too many protons. They tend to become more stable by positron emission or electron capture.

© 2009, Prentice-Hall, Inc. Stable Nuclei There are no stable nuclei with an atomic number greater than 83. Nuclei with such large atomic numbers tend to decay by alpha emission.

Nuclei with low neutron-to-proton ratios tend to undergo __________ emission. 1. alpha 2. beta 3. gamma 4. positron

Nuclei with atomic numbers greater than 83 tend to undergo __________ emission. 1. alpha 2. beta 3. gamma 4. positron

Nuclei with high neutron-to-proton ratios tend to undergo __________ emission. 1. alpha 2. beta 3. gamma 4. positron

Uranium Decay Cards Find and lay out the first 4 naturally occurring decay reactions for Uranium Graph the first 4 elements with atomic number vs mass.

Ionizing vs Non-ionizing radiation

Penetration Lab

Particle Details

How we protect ourselves Time/Exposure Distance Shielding

Half Life Definition Every radioisotope has a characteristic rate of decay. Half Life – the time required for ½ of the nuclei in the sample to decay to its products.

Half life problem – “easy” example The half-life of is 12.4 hours. How much of a 750 g sample is left after 62.0 hours? 23.4 g is left after 62.0 hours.

A 50.0 g sample of decays to 12.5 g in 14.4 seconds. What is its half-life? Push any number, then hit the pencil button, enter your answer, then hit the enter button to submit your answer

Oxygen-15 is used as a radioactive tracer in medical imaging and has a half-life of 2.0 min. If the initial concentration of 15 O is 16 mM, how long will it take for the concentration to be reduced to 1 mM ? 1. 4 min 2. 6 min 3. 8 min min min

Half life lab Half life of Pennies Dice half life

1 st order kinetics - equation

Fission vs Fusion Fission – splitting of atoms to form smaller nuclei Fusion – joining of atoms to form larger nuclei Both produce lots of energy but fusion far more than fission

© 2009, Prentice-Hall, Inc. Nuclear Transformations Nuclear transformations can be induced by accelerating a particle and colliding it with the nuclide.

© 2009, Prentice-Hall, Inc. Particle Accelerators These particle accelerators are enormous, having circular tracks with radii that are miles long.

Other good ideas Virtual tour of nuclear power plant webquest Debate the benefits vs risks of nuclear power Cloud chambers to “see” radiation Carbon dating activity puzzle Explore medical uses of nuclear chemistry

Cloud Chambers Tracks of ionizing radiation in a cloud chamber (thick, short: alpha particles; long, thin: beta particles).

G Hope you enjoyed! Send your feedback. Michelle Robinson