Nuclear Chemistry

1
Nuclear Chemistry

• ALPHA-Chemistry I-B
• Chapter 28

2
Wilhelm Roentgen

• Wilhelm Roentgen
• Discovered X-rays
• Was awarded a Nobel Prize for the discovery of
  the mysterious rays

3
Henri Becquerel

• Henri Becquerel was a part of the group that
  made a the early discoveries of radiation.

4
Marie Curie

• Marie Curie and her husband made the discovery of
  radiation.
• She was awarded two Nobel Prizes for her work.

5
The Discovery of Radiation

• Henri Becquerel (1895) discovered that pitchblend
  (Uranium ore) would expose film. He called it
  radioactivity.
• Marie and Pierre Curie worked long difficult
  hours and discovered new elements-Radium and
  Polonium

6
Nuclear vs. Ordinary Reactions

• Ordinary chemical changes (the ones that display
  our indicators of chemical reactions) only
  involve electrons.
• Nuclear changes involve the nucleus and create
  new atoms.
• Larger atoms are from fusion
• Smaller atoms are from fission

7
Radiation

• Radioactivity or Radiation is the spontaneous
  emission of alpha, beta, or gamma rays the
  disintegration of the nuclei of atoms.

8
Types of Radiation

• Alpha particles
• A helium atom doesnt have any electrons
  positively charged.
• Beta Particles
• A very fast moving electron
• Negatively charged
• Gamma Rays
• A form of energy lots of energy that moves in
  waves
• The rays go through a lot of materials.

9
Going for the Block

• Alpha particles can be blocked by a piece of
  paper however, once inside the body the most
  immediate damage.
• Beta particles can be stopped with a piece of Al
  foil. They do more damage over a great area of
  the body.
• Gamma rays penetrate most things and do the most
  damage to DNA.

10
Radiation Protection

1. Distance
2. Time
3. Shielding

11
Nuclear Protective Gear
12
Nuclear Equations-Know your particles and all is
easy

• Alpha particles -changes the mass number by four
  and the atomic number by two. Its a Helium
  nucleus
• Beta Particles -changes the atomic number by one.
  No change to the mass number.
• Neutron -no change to the mass number, but the
  mass changes by one.

• Alpha Particle
• Beta Particle
• Neutron

These are the main ones !!!!!!
13
The other particles

• Proton
• Positron

14
Five types of nuclear change

1. Alpha Decay
2. Beta Decay
3. Gamma Decay
4. Fission (spitting)
5. Fusion (joining)

15
Nuclear Equations

• Both sides of the equation must be equal in both
  mass number and atomic number!
• Its just very easy algebra!

16
Examples
17
Word Problem Example

• Thorium-225 undergoes alpha decay. Write a
  balanced equation for the reaction.

18
Decay Series

• A continuous flow of nuclear decay.

19
Fission reaction

• Nuclear fission is when nucleus is split into two
  smaller nuclei.

20
Fusion

• Fusion is when two nuclei join to form a larger
  nucleus. The same reaction occurs in the sun!

21
A Fission Reactor

• Cannot explode like a nuclear bomb. Uses a
  different form of uranium-238
• There is actually less pollution that goes into
  the air.
• Nuclear weapons use uranium-235

22
Half-Life

• Half life is defined as the time it takes for one
  half the mass of the radioactive isotope to
  become stable (non-radioactive)
• Substances with short half-lives can cause more
  health hazards than isotopes with long half-lives
  (radiation is given off much more slowly.)
• We are going to view an animation
• http//library.thinkquest.org/27948/decay.html

23
Half-Life Terms

• The portion that remains radioactive is called
  the parent
• The decayed portion is called the daughter.
• The daughter is not usually radioactive, but it
  can be.

24
Examples

• Carbon-14 has a half-life of 5700 years. How much
  remains of a 600 gram sample after 17,100
  years?
• Polonium-210 has a half-life of 138.4 days. How
  much remains of a 1000 gram sample after 98.86
  weeks.

25
Calculating half-life

• The fraction of the original amount that remains
  is still radioactive.
• The easy way
• Determine the number of half-lives
• Divide the mass by 2 until you have divided as
  many times as you have number of half-lives
• The Formula

26
Carbon Dating

• Carbon-14 and Nitrogen-14 are used to date items
  based on the half-life of carbon-14.
• We know it takes 5730 years to decay carbon-14.
• The amount present in the atmosphere is constant.
  So you just measure whats in the artifact and
  work backwards.

27
Measuring Radiation-read only

• RadRadiation Dose
• Rankinrad/hour
• REMroentgen equivalent man
• 1/1000 rem 1 mrem
• LETLinear energy transfer
• A rad is the amount of energy that is released in
  tissue when it is irradiated. One rad100 ergs
  (energy uints) deposited in one gram of tissue.

28
REM-read only

• A REM measures the biological effect of radiation
  on the human body without having to worry about
  the type of radiation involved.
• Whats allowed? 5-10 rems per year. Its very rare

29
When radiation hits a cell-read only

• It may pass through the cell w/o damage.
• It may damage the cell, but the cell fixes the
  damage.
• It may damage the cell the cell reproduces the
  damaged form.
• The cell dies-serious problems occur if too many
  cells are killed in a certain organ.

30
Guidelines-read only

• From WWII Studies
• 650 rads Death within a few hours
• 300 rads Lethal-death in 60 days
• 50-250 rads Radiation sickness
• Symptoms of radiation sickness
• Nausea, vomiting, diarrhea, hair loss, sore
  throat, reduction in blood platelets, bone marrow
  damage
• Delayed effects Cancer, leukemia, cataracts,
  sterility, decreased lifespan