Download Isotope Half-Life Radiation Emitted

Marie Curie
Nuclear Chemistry—chemistry
of the nucleus
http://www.chem.orst.edu/graduate/pics/Reactor.jpg
How does a nuclear reactor work?
http://www.lanl.gov/science/1663/images/reactor.jpg
How does a small mass contained in
this bomb cause……
• Nuclear Bomb of
1945 known as “fat
man”
http://www.travisairmuseum.org/assets/images/fatman.jpg
…this huge nuclear explosion?
http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg
Is there radon in your basement?
http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg
A.
I. Radiation/Radioactivity
What is it?
1. The release of energy and/or matter from the nuclei of
atoms.
2. If something is radioactive it is giving of energy or particles
3. Radioactive decay = the spontaneous break down of an
atom’s nucleus; may cause the atom to to turn into a
different kind of atom.
• B. Review of atom
• 1. nucleus contains protons & neutrons & electrons spin
• around nucleus
• 2. proton mass = ____ neutron = ____ electron = ___
• 3. proton charge =____ neutron = _____ electron = ___
• 4. atomic # = ________
• 5. atomic mass = ______ + _______
• 6. Isotopes: atoms with the same # of protons, but different
number of neutrons than mass number.
Notation
H
H
H
http://education.jlab.org/glossary/isotope.html
Isotopes of Carbon
C. Why are atoms radioactive?
1. The nucleus is unstable due to imbalance of protons and
neutrons or a large # of neutrons and protons.
2. The strong force (holds the neutrons and protons together) &
weak force (holds protons together) are not strong enough.
• 3. elements with atomic # > 83 = radioactive
II. Main Types of Radioactive Decay
•Alpha
a
•Beta
b
•Gamma g
A. Alpha Decay
* Emission of alpha particle -- a :
• Nucleus releases a particle that is 2 protons & 2
neutrons = Helium nucleus. (4 amu, 2+ charge)
• Proton # deceases by 2 & mass decreases by 4
• Notation:
• can travel a few inches through air
• can be stopped by a sheet of paper, clothing.
Alpha Decay
http://education.jlab.org/glossary/alphadecay.gif
Alpha Decay
B. Beta Decay
• Emission of Beta particles b
• electrons ejected from the nucleus when neutrons decay into a proton.
• Proton # increases by 1, mass stays same.
• Notation:
• Can be stopped by aluminum foil or a block of wood.
Beta Decay
Beta Decay
C. Gamma Decay
• Emission of Gamma radiation-- g
• Gamma rays are electromagnetic waves or energy
• They have no mass.
• Gamma radiation has no charge.
• Most Penetrating, can be stopped by 1m thick concrete or a several cm thick
sheet of lead.
Examples of Radioactive Decay
Alpha Decay
Po 
Beta Decay
C 
Gamma Decay
Ni 
Band of Stability
Number of Neutrons, (N)
Number of Protons (Z)
III. Radioactive Half-Life :
A. What is it:
1. The time it takes for half of a radioactive
sample of atoms to change into something
else.
2. represented by t1/2
3. After one half -life there is 1/2 of original
sample left.
4. After two half-lives, there will be
1/2 of the 1/2 = 1/4 the original sample.
Half-life of some isotopes
Isotope
Half-Life
Radiation
Emitted
Carbon-14
5,730 years
b, g
Radon-222
3.8 days
a
Uranium-235
7.0 x 108 years
a, g
Uranium-238
4.46 x 109 years
a
Example
You have 100 g of radioactive C-14. The half-life of C-14 is 5730 years.
• How many grams are left after one half-life?
• How many grams are left after two half-lives?
Problem
A sample of 3x107 Radon atoms are trapped
in a basement that is sealed. The half-life of
Radon is 4 days. How many radon atoms
are left after 32 days?
B. Half-life Graphs
1. Can use graph to figure out half-life of an atom
2. As the parent isotope decreases the daughter
isotope increases
C. Uses of Radioactive dating
1. Dating Fossils
2. Dating rocks
3. Finding a safe isotope to put in someone’s body
4. Determining when it is safe to go somewhere that there has been
Radiation.
IV. Fission
A. Splitting of an atomic nucleus into 2 smaller nuclei with the
release of a large amount of energy and radiation.
1. Then energy is from the forces that held the nucleus together
and also lost mass.
2. E= mc2– Einstein’s equation
Energy = mass x the speed of light2
There is the loss of some mass that is
converted into energy
3. Nuclear chain reaction: continuous series
of fission rxns.
* as one nucleus splits,
neutronsAre released to split more
nuclei
B.Uses of fission
1. Nuclear
power plants– use fission of Uranium-235 to create
heat that create steams that turns a turbine that is used to
create electricity.
2. Nuclear weapons: use fission
to create immense
amounts of energy (an explosion)
to destroy people
Critical mass: amount of U-235 that will sustain a chain reaction.
VI. Uses/Exposure to Radiation
A.Uses
1. Fission– nuclear energy
2. Alpha/beta/gamma particles/rays:
a. Sterilize food (kill microorganisms)
b. detect leaks in pipes
c. Medical uses (imaging, detecting disease, tracing
Blood circulation, treating cancer
B. Exposure
A.Background radiation
All around us from stars, rocks, etc.
Earth’s atmosphere and magnetic field
stops most of the cosmic radiation.
B.Other sources
X-rays, other medical procedures,
nuclear accidents
V. Fusion
A. The joining of 2 small atomic nuclei to
form a single nucleus releasing a large
amount of energy and radiation.
1. Need temps of millions of degrees Celsius
2. Occurs naturally on/in stars
3. Attempting to use it here
for energy—but many problems
4. Occurs mostly with Hydrogen Atoms (lightest atoms)
(drawing)
A. Energy Source
1. Fusion: Hs fuse to make He
2. Produces huge amounts of light and heat
B. Properties
1. Color & 2. Temperature—blue (hot!!) red (cool) , yellow
(medium), White (cool)
3. Brightness—affected by size and surface temperature
---if something is closer, it appears brighter
---Real brightness can be calculated
4. Size/Mass—cannot be measured directly, brightness is used
C. Hertzsprung-Russell Diagrams
1. Graph that helps classify stars
2.Used to estimate size, brightness, temp,
distance, and changes in stars.
D. Life Cycle of Stars
1. Star Formation
a. Nebula
b. Protostar
c. Star
E. Star Death
1. Stars change when the H runs out
2. Now He starts to fuse
3. More mass = increased gravity