NAME: ____________________________________________ DATE: __________________ PERIOD: ________
8.3 Radiometric Dating Practice Problems
Radioactive Parent Isotope
Rubidium-87 (Rb-87)
Thorium-232 (Th-232)
Potassium-40 (K-40)
Uranium-238 (U-238)
Uranium-235 (U-235)
Carbon-14 (C-14)
Approximate Half-life
48.6 billion years
14.0 billion years
1.3 billion years
4.5 billion years
0.7 billion years
5730 years
Daughter Product
Strontium-87 (Sr-87)
Lead-208 (Pb-208)
Argon-40 (Ar-40)
Lead-206 (Pb-206)
Lead-207 (Pb-207)
Nitrogen-14 (N-14)
% of Parent Element (C-14)
100
50
% of Daughter Element (N-14)
% of Parent Element (U-238)
100
% of Daughter Element (Pb-206)
# of Parent Element (K-40)
# of Daughter Element (Ar-40)
Number of Half-Lives
Elapsed Years
# of Parent Element (U-235)
# of Daughter Element (Pb-207)
Number of Half-Lives
Elapsed Years
Number of Half-Lives
Number of Half-Lives
Elapsed Years
Elapsed Years
Name: __________________________________________________ Period: ______ Date: _______________
Radioactive Parent Isotope
Rubidium-87 (Rb-87)
Thorium-232 (Th-232)
Potassium-40 (K-40)
Uranium-238 (U-238)
Uranium-235 (U-235)
Carbon-14 (C-14)
Approximate Half-life
48.6 billion years
14.0 billion years
1.3 billion years
4.5 billion years
0.7 billion years
5730 years
Daughter Product
Strontium-87 (Sr-87)
Lead-208 (Pb-208)
Argon-40 (Ar-40)
Lead-206 (Pb-206)
Lead-207 (Pb-207)
Nitrogen-14 (N-14)
1) How old is a rock sample that is composed of 50% Nitrogen-14 (N-14) daughter products?
2) How old is a rock sample that is composed of 93.75% Lead-208 (Pb-208) daughter products?
3) How old is a rock sample that is composed of 12.5% Rubidium-87 (Rb-87) parent isotopes?
4) How old is a rock sample that is composed of 75 Potassium (K-40) parent isotopes and 525 Argon-40 (Ar-40)
daughter products?
5) A rock containing 150 Uranium-235 (U-235) is 2.1 billion years old. How many daughter products does it
contain at this point?
6) How many parent isotopes would a rock containing 1024 total isotopes have if it has gone through 10 halflives? Can you determine the age of this rock? Explain.
SCIENCE
OPEN-ENDED ITEM
A.1.3.2
This is a short open-ended (SOE) questions. It is worth two points.
12 Scientists use parent to daughter isotope ratios to determine the age of certain rocks and objects. Say you
discover a bone in a park near your home. After being analyzed in a lab, it is has been determined that the
bone contains 87.5% Nitrogen-14.
Radioactive Parent Isotope
Rubidium-87 (Rb-87)
Thorium-232 (Th-232)
Potassium-40 (K-40)
Uranium-238 (U-238)
Uranium-235 (U-235)
Carbon-14 (C-14)
Approximate Half-life
48.6 billion years
14.0 billion years
1.3 billion years
4.5 billion years
0.7 billion years
5730 years
Daughter Product
Strontium-87 (Sr-87)
Lead-208 (Pb-208)
Argon-40 (Ar-40)
Lead-206 (Pb-206)
Lead-207 (Pb-207)
Nitrogen-14 (N-14)
Work Area:
Part A: Use the table above to determine the absolute age of the bone.
The bone’s absolute age is _____________ years.
Part B: Explain why the bone’s age can be determined by knowing the percent of Nitrogen-14.
Why bone’s age can be determined: _____________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________
___________________________________________________________________________________________.
Total Isotopes
# of Parent Element
# of Daughter Element
# of Half-Lives
Elapsed Years