Week 15

After the third half-life, how much of the sample is left?

• 1/2
• 1/3
• 1/16
• 1/8

If 10 mg of iodine 131 is given to a patient, how much is left after 24 days? The half-life of iodine-131 is 8 days.

• 1.25mg
• 1.25g
• 10g
• 10mg

The half-life of strontium-90 is 25 years. How much strontium-90 will remain after 100 years if the initial amount is 4.0 g?

• 3.0g
• 0.25mg
• 0.3g
• 0.25g

If the half-life of uranium-232 is 70 years, how many half-lives will it take for 10 g of it to be reduced to 1.25 g?

• 1 half-life
• 2 half-lives
• 3 half-lives
• 4 half-lives

What type of decay is being illustrated in following picture? 

• beta decay
• alpha decay 

You have 100 grams of radioactive C-14. The half life of C-14 is 5730 years. 
How many grams are left after 1 half life? 

• 100 grams
• 25 grams
• 2 grams
• 50 grams

What is Half-life?

• The amount of time it takes for some of the nuclei in a sample of the isotope to decay
• The amount of time it takes for half the electrons in a sample of the isotope to decay
• The amount of time it takes for half the nuclei in a sample of the isotope to decay
• the amount of time it takes to double the nuclei in a sample of the isotope to decay

During beta decay, a nucleus .... 

• gives up two protons and two neutrons.
•   maintains the same number of protons and neutrons.
•   loses a proton and gains a neutron.
• gains a proton and loses a neutron. 

The process of the production of lighter nuclei from heavier nuclei is called

• mass energy
• magneticism
• fusion
• fission

The process by which nuclei having low masses are united to form nuclei with larger masses is ____.  

• a chain reaction 
• fission
• a chemical reaction 
• fusion