Unit 2 Review

How long does it take a 180-gram of gold-198 to decay to 22.5 grams if the half -life of gold-198 is 2.68 days?

• 8.04 days

• 3 days

• 4 days

• 2.68 days

The nucleus is held together by the ___________________________force.

• The Strong Nuclear Force

• The Weak Nuclear Force

• Electromagnetism

• Gravity

Has the highest penetrating power.  Can penetrate our body.  Even several cm thick of lead or several meters thick of concrete cannot stop all of it.

• Alpha
• Beta
• Gamma

Has a mass of 4 and a charge of +2

• Alpha
• Beta
• Gamma

Has the lowest penetrating power.  Can only penetrate 0.05 mm into the body and can be stopped by a piece of paper or clothing.

• Alpha
• Beta
• Gamma

How is the alpha particle written in a nuclear equation?

• ⁴₂He

• ²₄He

• ⁰_-1e

• ⁰₀γ

Cobalt-60 can be used by scientists for the purpose of radioactive dating. Cobalt-60 has a half-life of 5,272 years. A fossilized rock originally contained 25 grams of Co-60. When tested, the rock only contains 6.25 grams of Co-60. Approximately how old is the item?

• 2,600 years

• 10,500 years

• 5,600 years

Atoms of element A decay to atoms of element B with a half-life of 20,000 years. If there are 10,000 atoms of A to begin with (and 0 atoms of B), how long will it take for there to be 2,500 atoms of A?

• 20, 000 yr

• 40, 000 yr

• 60, 000 yr

• 80, 000 yr

How many oxygen atoms are in this chemical formula?

• 6 oxygen atoms

• 2 oxygen atoms

• 3 oxygen atoms

• 4 oxygen atoms

What is the arrow in a chemical equation...
H_{2 +} O --> H₂O

• Reactants
• Products 
• Yields 
• Chemical Equation