1. Review and Radioactivity

2. Review Atomic # = # P = # e Isotope…same p/e…different # of neutrons
form electrically neutral atom
If # P does not equal #e then it is called an ION
Isotope…same p/e…different # of neutrons
ex - C12 or C14 as is mass #
You can determine valence e- by the group number on Periodic Table
Properties of Metals vs. Nonmetals
Elements with full valence electron shells are STABLE

3. Radioactivity
Nucleus contains almost all the mass of an atom (p/n have all mass)…electrons are negligible (little mass)
EX. Marble sitting in middle of football field
Nuclear decay/Radioactive decay – When unstable nuclei decay particles and energy (called nuclear radiation) are emitted (given off)
This happens spontaneously (naturally)
Occurs mostly in large elements because large nuclei are unstable and decay more than small nuclei
attraction forces aren’t as strong to hold particles within nucleus

4. Nuclear Decay 3 types of nuclear radiation A. Alpha-particles
B. beta-particles
C. gamma-electromagnetic wave

5. Alpha Particle Helium nucleus is emitted (2 p/2 n) Charge =+2 Mass = 4
LARGEST
Least energy
Least penetrating power - stopped by paper
Dangerous if swallowed or inhaled (Radon gas)
Transmutation occurs

6. symbol

8. Beta particle Particle An electron is emitted (given off) Charge is -1
mass is (very small)
More energy than alpha
Goes thru paper….stopped by foil
Penetrates skin and nerve cells
Transmutation occurs

9.
I e- = Xe

10. Gamma Rays Waves No mass and no charge
Most powerful and penetrating of all
Lead and concrete can stop gamma rays
Passes through body – can cause or cure cancer
Transmutation does NOT occur

13. Half-life
Half-life - The amount of time a radioactive isotope takes for half the nuclei of a sample to decay
Steps:
Set up your chart (EVERYTIME)!
Fill in your ZEROS.
Fill in what you already know.
Calculate what you don’t know.
a) Amount – divide by 2
b) Time – add another half life
Use the chart to answer the question.

14. Half Life Table

15. Problems examples
The half life of calcium is 10 days. How much of a 100 g sample will remain after
1) 20 days?
2) 30 days?
3) 40 days?
4) 50 days?

16. Another look
A sample of Phosphorous-18 originally has 30g. Phosphorous-18 has a half life of 2,000 years. In years, how many grams would remain undecayed?
1) 4,000 yrs
2) 8,000 yrs

17. Another look
At the end of 45 days, 100 g of Carbon-14 has decayed to 12.5 g. What is the ½ life of Carbon 14?

18. What is the half life of the radioisotope?
Gieger counter data
Time in days
0.0
5.0
10.0
15.0
Counts per second
1000
2000
3000
4000
What is the half life of the radioisotope?

20. Type? Transmutation?

21. FUSION AND FISSION

22. THE SUN
Every second, the sun converts 500 million metric tons of hydrogen to helium. Due to the process of fusion, 5 million metric tons of excess material is converted into energy in each second. This means that every year, 157,680,000,000,000 metric tons are converted into energy.

23. Nuclear Fusion
Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus.
It is accompanied by the release of energy

24. FUSION
DEUTERIUM
NEUTRON
HELIUM
TRITIUM

25. Fusion Changes Mass to Energy E=mc2
.993 kg Helium He H
1kg Hydrogen

26. NUCLEAR FISSION
A reaction in which a nucleus of a radioactive element splits by bombardment from an external source, with simultaneous release of large amounts of energy, used for electric power generation

27. Nuclear Fission Neutron induced in U235 Fission is Exothermic
The sum of the masses of
the resulting nuclei is less
than the original mass (about 0.1% less)
The “missing mass” is converted to energy according to E=mc2

28. Review Nuclear fission:
A large nucleus splits into several small nuclei when impacted by a neutron, and energy is released in this process
ENERGY GENERATION
Nuclear fusion:
Several small nuclei fuse together and release energy.
THE SUN