Drill – 10/21

• Clear desk of everything and take outline, ½ sheet of paper, and pen or pencil out

Pop Reading Quiz

1. What is the energy released when a nucleus is formed from nucleons called?

2. The band of stability shows that at low atomic numbers the most stable elements are those with what neutron to proton ratio?

3. Give an example of a nuclear equation

4. Give the 5 types of radioactive decay

5. What is half-life?

Objective

• SWBAT explain how some isotopes are made of unstable nuclei that decay over time emitting particles and energy.

• SWBAT contrast alpha, beta, & gamma emissions, the composition of each, and the material required to shield them.

• SWBAT balance a nuclear equation.

Alpha, Beta, & Gamma Radiation

• Measured by passing radiation through electrically charged plates.

Alpha Radiation α

• Deflected towards the negative plate…so POSITIVE.

• Alpha particles are a Helium nucleus – with 2 protons and 2 neutrons

He4

2

Alpha Radiation α

238 234 4 U Th + He

92 90 2Uranium-238 Thorium-234 Alpha Particle

Note that the mass number always decreases by 4 after the alpha emission. Atomic number decreases by 2

Beta Radiation β

• Deflected towards the positive plate…so NEGATIVE

• Beta particles are fast-moving negatively charged electrons

β0

-1

Beta Radiation β

• How is it possible to lose an electron from the nucleus?

Neutrons are theorized to be made up of a proton and an electron.

1 1 0 n H + e 0 1 -1

A neutron is changed into a proton and an electron and the electron is emitted.

Beta Radiation β

234 279 0 Th Pa + e 90 91 -1

Thorium-234 Beta particle

By combining the charges from the bottom of the two symbols, figure out the symbol for the remaining particle

?

Beta Radiation β

234 234 0 Th Pa + e 90 91 -1Thorium-234 Beta particle

By combining the charges from the bottom of the two symbols, figure out the symbol for the remaining particle

Pa

Protactinium-234

Gamma Radiation γ

• Not deflected by charged plates…so NO CHARGE

• Gamma rays are high-energy electromagnetic radiation (like u-v or radio or x-rays) with no mass

• They have very SHORT wavelength

• They have HIGH energy

γ0

0

http://www.whfreeman.com/chemcom/content.htm#

10/22

• How many milligrams of a 15.0 mg sample of radium-226 remain after 6300 years? The half-life of radium-226 is 1599 years.

10/22

• The half-life for radium-224 is 3.66 days. What was the original mass of radium-224 if 0.0500g remain after 7.76 days?