1. Will not take any after next Tuesday 1/13

Late Work?

1. Define each of these terms: You may use your notes and they do not need to be in complete sentences

EnergyHalf-life Law of Conservation of Matter Fusion Fission

2. Which is represented below alpha, beta, or gamma decay?

238 U 238 Nb + 0 e

ABSENT YESTERDAY?Entry Task

92 99 -1

1. GRAPH HOW WELL YOU DID ON YOUR ENTRY TASK AND WORKSHEET AFTER YESTERDAYS DISCUSSION

UPDATE YOUR GOAL SHEET

Electromagnetic Spectrum

Which is more penetrating? Why?

Higher Energy and Frequency

Alpha decay occurs only in heavier elements of atomic number 52, tellurium, and greater.

Beta & Gamma were seen in all of the elements.

Radioactive decay is seen in all isotopes of all elements of atomic number 83.(Wikipedia)

Nuclei with atomic number > 83 are radioactive

How do you know which type of decay will occur?

•Nuclear Stability •Half-Life

http://imperfectionists.wordpress.com/

When do we get alpha decay?

• A nucleus decays because it is unstable. • The daughter nucleus is more stable than

the parent• So you will not have the same element

after the parent material decays

• Decrease of Protons & Neutrons by 2

Alpha Decay

Uranium Thorium

Alpha Particle

• What are the products of Carbon going through alpha decay

Turn and talk, document in notebook

• Lets write it out

When do we get beta decay?• Occurs in a nucleus w/ too many protons

or too many neutrons• When decays also gives off an e- (no

mass, neg. charge) called a beta particle

• The resulting reaction is the same mass, but an increase of one proton• How?

When do we get beta decay?• Neutrons are composed of 1 e- & 1 proton• Neutron decays to release 1 e- what do you

have left?

One Proton

Beta Decay

Thorium Protactinium

Beta Particle

• What are the products of Carbon going through beta decay

Turn and talk, document in notebook

• Lets write it out

When do we get gamma decay?• a nucleus changes from a higher E state to a

lower E thru the release of EM radiation (photons).

• The # of protons (and neutrons) in the nucleus doesn’t change, so parent and daughter are same element

•Half-Life

http://imperfectionists.wordpress.com/http://www.physics.isu.edu/radinf/half.htm

Common Radioactive Isotopes

Isotope Half-Life Radiation Emitted

Carbon-14 5,730 years β, γ

Radon-222 3.8 days α

Uranium-235 7.0 x 108 years α, γ

Uranium-238 4.46 x 109 years α

Radioactive Half-Life

• After one half life there is 1/2 of original sample left.

• After two half-lives, there will be

1/2 of the 1/2 = 1/4 the original sample.

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?

Answer: 50 g

Answer: 25 g