Atomic Structure
The atom, it's parts, and how it all works.
Dr. Melinda Oliver
Bishop State Community College
First, a little history.
Dalton's Model
Thomson's Model
Rutherford's model
Let's focus on the nucleus
Mass number and atomic number
A little practice
Average Atomic Mass
Bohr's Model
Bohr's model pictured like the solar system
Our current model (Quantum Mechanical model)
Know all of the group names on this periodic table.
Radioactivity-unstable atomic nuclei
Alpha decay
Beta decay
Gamma rays
One of the four fundamental forces in nature is the Strong Nuclear Force
The mass defect-the most famous science equation!
You have learned that in chemical reactions, mass is conserved. For the most part, this is correct. There are very minimal mass differences that using Einstein's famous equation would translate into small amounts of energy. That is what the equation is about-the direct relation between mass and energy. There is a great book on this equation. The history behind every piece (even the equal sign). For those interested:
So, in typical chemical reactions some of the mass (about 9.9 x 10^-9 g for the combustion of one mole of methane) is lost but this is pretty minimal. However, plug it into the equation and you do get some energy out of it.
The mass lost in nuclear reactions is much larger. For a typical alpha emission:
the mass lost (product mass-reactant mass) is -0.0046 g. Plug this into the equation (convert mass into kg so energy comes out in joules) and you end up with -4.11 x 10^11 J, a pretty significant amount of energy.
Half-Life
Fission
Fusion
Answers to Questions above
5. 120 yr
6. 1/16
7. 127.5 g
Some hints for solving half life problems
If the problem is asking for "how long ago" or "how much time", MULTIPLE # of half lives by the time for one half-life. (#5 above)
If the problem is asking for "how much of the radioactive stuff is left", multiply the fraction (obtained by # of half lives that have passed) by the original amount of the radioactive stuff. (#'s 4, 6, 7 above)
Useful chart for radioactive symbols and half-lives.
What Else Can You Do to Help Your Understanding?
Have Questions Later?
Dr. Melinda Oliver
Bishop State Community College
Email: moliver@bishop.edu
Location: Mobile, AL, United States
Phone: (251)405-4504