GEMS 1604703

1
GEMS 160 4/7/03

• Ch. 10 exam avg 60/72 - key on discussion board.
  Part 2 returned on Wednesday ??
• Tuesday lab time for topic research
• Poster topics on discussion board
• Abstract due Tuesday (1200 or 400) via e-mail
• Topic questions due Friday
• Chemistry news
• Today Ked Pomeroy
• Wednesday Mandy Smits, Nate Olson
• Continue chapter 4 today

2

• Ked Pomeroy -
• A Major Chemical spill into two Brazil rivers has
  cut off water supply to half a million people
• A wood-pulping factory started leaking caustic
  soda (sodium hydorxide) and chlorine into the
  Rarida de Sul, Rio de Janiero's main River
• More than 1.2 billion litres emptied into the
  river
• The rise in pH may have killed hundreds of
  plants, animals, and fish
• The sodium hydroxide is used at a 50
  concentration and has a pH of 14 at that level. A
  10 solution will eat the skin right off your
  body.
• If the water can be isolated it can be it can be
  treated with dilute hydrochloric acid or acetic
  acid

3
Any one interested in the artifacts of ancient
cultures? Who has known someone who has undergone
radiation treatments for cancer? Who lives within
50 miles of a nuclear power plant? Who has
recently heard about nuclear weapons of mass
destruction? All related to nuclear chemistry
!! Which of the following are not related to
nuclear reactions - why or why not ?? ? ? ?
? ? What is radioactivity ??
4
Natural radioactivity

• Tritium decays by ? emission - what does this
  mean?
• What is tritium?

• What is ? decay?

• Must always have mass balance. What else must be
  present with the ? ?

5
Natural radioactivity

• Carbon -14 decays by ? emission - what does this
  mean?
• What is carbon -14?

• What is ? decay?

• Must always have mass balance. What else must be
  present with the ? ?

6
Natural radioactivity

• U-238 decays by ? emission - what does this mean?
• What is U-238?

• What is ? decay?

• Must always have mass balance. What else must be
  present with the ? ?

7
Chain of radioactive decay

• Emission of decay particle from an unstable or
  radioactive nucleus
• A new element is formed, which may or may not be
  stable.
• Unstable isotopes continue the decay chain until
  a stable, non-radioactive isotope exists
• Note the presence of radon gas in this chain
• Health hazard because the radon gas decays to
  polonium, which is a solid that is not exhaled.
• Further decay of ionizing radiation causes cell
  damage

8
Transmutation -unatural radioactive processes

• Nitrogen-14 is bombarded by alpha particles -
  what does this mean chemically?

• One of the observed particles is a proton, what
  is the other particle that is formed?

9
Complex nuclear chemistry

• Fact - like charges repel
• So - how do all the protons stay next to each
  other in the nucleus ??
• More complex than protons and neutrons
• Positron Antiproton
• Quark Gluon
• Flavor Color Charm
• Important for this course - nuclear stability is
  determined by the number of neutrons, and
  specifically the neutron/proton ratio

10
Neutrons, protons and stability

• For low atomic numbers, 11 (np) ratio is stable
• Deuterium is stable, tritium is not
• C-12 and C-13 are stable, C-14 is not
• For higher atomic numbers, 1.51 (np) ratio is
  stable
• Pb-208 is stable
• Generally, adding neutrons beyond this stable
  region leads to nuclear decay

11
Lise Meitner and Otto Hahn

• Hahn added neutrons to the uranium nucleus -
  observed barium !!
• Interpreted by Meitner as splitting of an
  unstable nucleus gt nuclear fission
• Fission was very different than other nuclear
  reactions where a few small particles were
  observed - there was an enormous release of
  energy !!
• At a time of pending war the quest for energy -
  explosive energy - was heightened