Embed Size (px)
Citation preview
Unit 17Radioactive Decay
Unstable Atoms
When the repulsive forces of the protons exceeds the ability of the strong nuclear force to hold them together, they are unstable.
In addition, sometimes nuclei are too heavy and have too many neutrons to remain together
Three Types of Radiation
Alpha Particles- 2 protons and 2 neutronsBeta Particles- electronGamma Rays- Tiny electromagnetic waves
Alpha Particles
* Represented by α (alpha)
* They are equivalent to the nuclei of a He atom
* (+2) Charge, heavy and slow moving
*Limited penetrating power, stopped by sheet of paper
Alpha Particles
* Represented by α (alpha)* They are equivalent to the nuclei of a He atom* (+2) Charge, heavy and slow moving*Limited penetrating power, stopped by sheet of paper
Equation Example:
Conversion From One Element to Another Through Alpha Decay
Dangers of Radon Gas
Radioactive Decay Series
Radioactive Decay Series
Radioactive Decay Series
Radioactive Decay Series
Radioactive Decay Series
Beta Particles
Represented by β (beta)
(-) Charge, little mass, 100x faster than alpha
Basically high-speed electrons
Stopped by Aluminum Sheet.
Changes a Neutron into a Proton
Beta Particles
Equation Example:
Beta Decay Series
Beta Decay Series
Beta Decay Series
Beta Decay Series
While it may seem it is cycling around, the difference is it keeps losing mass, thus it turns from Ra-228 to Ra-224
Gamma Particles
Represented by ɣ (gamma)
Electromagnetic wave, no charge (neutral) or mass
Great speed, high-energy, very dangerous
High penetrating power
Only lead can stop them
Radioactivity
Alpha, Beta and Gamma Particles
Half-Life
Half-life is a measure of the rate of decay of a radioactive element.
It is the time it takes for half of the atoms to decay.
Number of Half Lives
Amount Remaining
Time
0 1
1 ½ 5,730 years
2 ¼ 11,460 years
3 1/8 17,190 years
4 1/16 22,920 years
5 1/32 28,650 years
Carbon-14 has a half life of 5730 years
Carbon-14 Dating
Number of Half Lives
Amount Remaining
Time
0 1
1 ½ 5,730 years
2 ¼ 11,460 years
Half Lives Vary Dramatically with Isotopes
Radioisotope Half-Life
Polonium-215 0.0018 seconds
Bismuth-212 60.5 seconds
Sodium-24 15 hours
Radon-222 3.82 days
Iodine-131 8.07 days
Cobalt-60 5.26 years
Radium-226 1,600 years
Uranium-238 4.5 billion years
The lack of certain elements on Earth is related to their very short half-lives
