An Introduction to Nuclear Chemistry : An Introduction to Nuclear Chemistry
How do you pronounce N-u-c-l-e-a-r? : How do you pronounce N-u-c-l-e-a-r?
What you’ve learned so far… : What you’ve learned so far… What are atoms?
What do you know about atomic structure?
What are ions?
What are isotopes?
Using what you know… : Using what you know… What is radioactivity?
What are nuclear reactions and how are they different than most chemical reactions we study?
What makes something radioactive?
Where do we see radioactivity around us?
Is it dangerous to us?
What are nuclear bombs and how do they work?
The story of radioactivity… : The story of radioactivity… Roentgen and cathode ray tube
~1900 Becquerel’s keys
What is radioactivity? : What is radioactivity? The spontaneous emission of high-energy radiation.
Radioisotopes- unstable isotopes that are radioactive Uranium glass
What is radiation? : What is radiation? Subatomic particles or waves (light)
3 types
Alpha - are helium nuclei emitted from radioactive atom.
Beta- fast moving electrons formed by decomposition of a neutron of an atom.
Gamma- high energy electromagnetic radiation
Characteristics of types of radiation : Characteristics of types of radiation Alpha particle Beta particle Property Alpha radiation Beta radiation Gamma radiation Composition (Helium nucleus) (electron) High-energy
electromagnetic
radiation Symbol a, ß ? Charge 2+ -1 0 Mass 4amu 1/2000 amu 0 Source Radium-226 Carbon-14 Cobalt-60
Charge of types of radiation : Charge of types of radiation
Penetrating power of 3 types of radiation : Penetrating power of 3 types of radiation
What makes something radioactive? : What makes something radioactive? Unstable nuclei (repulsion between protons in nucleus)
Proton to neutron ratio (magic numbers)
for elements with atomic number < 20 the ratio is 1
for elements with atomic number >20 the ratio is ~1.5
Slide 12 : Number of neutrons Belt of stability
The Belt of stability : The Belt of stability N
Ground state energy as a function of atomic number : Ground state energy as a function of atomic number
2 common ways of changing neutron:proton ratio : 2 common ways of changing neutron:proton ratio Beta decay
increase in protons, decrease in neutrons Alpha emission
decreases protons by 2 and neutrons by 2
Alpha emission : Alpha emission Alpha particle
Beta Decay : Beta Decay Beta particle
Half-life : Half-life Half-life - is the time required for one-half of the atoms of a radioisotope to emit radiation and to decay to products. 10g of radioactive
material 1 half-life 5g of radioactive
material 2nd half-life 2.5g of radioactive
material
Half-life problem : Half-life problem Nitrogen-13 has a half-life of 10 minutes. It emits beta radiation and decays to carbon-13. Assume a starting mass of 2.00g of nitrogen-13.
A) How long is four half-lives?
B) How many grams of nitrogen-13 will exist after three half-lives?
Half-life problem : Half-life problem A) 1 half-life is 10min. So four half-lives should be: 4 X 10min. = 40min.
B)You should map out this type of problem like this: 2.00g
N-13 1 half-life 1.00g
N-13 2nd half-life 0.50g
N-13 3rd half-life 0.25g
N-13
Try one on your own : Try one on your own How much of a 100.0g sample of Au-198 is left after 8.10 days if gold’s half-life is 2.70days?
A different type of problem : A different type of problem A 50.0g sample of N-16 decays in 12.5g in 14.4 seconds. What is N-16’s half-life?
….Try one more : ….Try one more The half-life of K-42 is 12.4 hours. How much of a 750g sample is left after 62.0 hours?
Where do we see radioactivity around us? : Where do we see radioactivity around us? nuclear power
Medical tracers
archaeology (dating)
radiation therapy
food preservation
weapons
Fission vs. Fusion : Fission vs. Fusion Fission
splitting nuclei
makes lighter elements
occurs at room temperature
releases energy
used in nuclear weapons Fusion
fusing nuclei
makes heavier elements
requires high temperature
releases more energy than fission
used in Hydrogen bombs
Fusion : Fusion Fusion- combining 2 elements together to form 1 heavier element.
Occurs in the Sun
Ideal energy source
abundant supply of Hydrogen
nonpolluting waste product.
Detecting Radiation : Detecting Radiation 3 ways:
Bubble chamber-ionized liquid or vapor.
Geiger counter-gas filled metal tube
scintillation counter-uses a specially coated surface.
film badge-photographic film
Why is radiation harmful? : Why is radiation harmful? The bubble chamber consists of a tank of unstable transparent liquid - often superheated hydrogen (which provides a source of proton targets). - in which passing charged particles initiate boiling as a result of the energy they deposit (by ionizing atoms) as they force their way through the liquid.
Slide 29 :
Slide 30 : Geiger Counters measure radiation levels
How does radiation effect the body? : How does radiation effect the body? Mild mannered David Banner was transformed
into a seven foot tall, green, raging beast after being exposed
to high levels of gamma radiation while saving a child from a
nuclear waste site
Health effects of radiation : Health effects of radiation What do you know about the effects of radiation on the body?
From what we’ve discussed so far, can you imagine a mechanism by which radiation could cause damage to your body? (take a couple minutes with the person next to you and come-up with some ideas)
Slide 33 : How do you feel about the idea of knocking electrons off the molecules in your DNA?
Your DNA is made-up of long chains of molecules linked together by Hydrogen bonds. Your body is mostly water. Ionising it results in OH- and H+ which leads to loss of cell vitality, decreased enzyme efficiency, causing cancers and genetic mutation. Radiation and your DNA
How much is dangerous? Dose effects : How much is dangerous? Dose effects The average x-ray delivers ~39mrem
Calculate your annual exposure to radiation : Compare your dosage to the average
~300mrem per year for 70 years gives 21,000mrem in a lifetime
Compare this to 100,000s mrem instantaneous exposure in Hiroshima bombing (140,000 died within 1 year) Calculate your annual exposure to radiation
Slide 36 :
What is a nuclear bomb? : What is a nuclear bomb? A weapon which gets its force from the energy released in nuclear fusion or fission reactions
Nuclear weapons : Nuclear weapons
Development of “the A-bomb” : Development of “the A-bomb” Discovery of neutron in 1932
Controlled fission of uranium pile 1942
Oppenheimer and the Manhattan project
Friends on opposite sides : Friends on opposite sides
How does a nuclear bomb work? : How does a nuclear bomb work? By bringing together a supercritical mass of uranium, a chain reaction is initiated which releases tremendous amounts of energy
fission of 1g of Uranium releases ~10million times more energy than burning 1g of coal
Nuclear fission : Nuclear fission U-235 + n -> fission + 2 or 3 n + 200 MeV
Chain Reaction : Chain Reaction
Supercritical mass : Supercritical mass
Little Boy design : Little Boy design Little Boy: A Gun-Type Bomb
Fat Man Design : Fat Man Design
Are nuclear weapons still used? : Are nuclear weapons still used?
Nuclear weapons today : Nuclear weapons today
Slide 49 :
For further reading : For further reading http://www.atomicarchive.com/Fission/Fission2.shtml
http://www.philrutherford.com/Radiation_Risk_LNT.pdf