unit 17 radioactive decay

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