1. I. Absolute Dating
A. The process of establishing the age of an object (fossil or rock layer) by determining how long it existed.

2. II. Radioactive Decay
The process by which radioactive isotopes break down into stable isotopes
Isotopes – atoms of the same element with the same number of protons but a different number of neutrons

3. III. Isotopes of Carbon Isotopes of Carbon Protons + Neutrons
Atomic Number & Stability
C12
6 P + 6 N
12 and stable
C13
6 P + 7 N
13 and unstable
C14
6 P + 8 N
14 and unstable

5. IV. HALF LIFE
A. The time it takes for ½ of a radioactive sample to decay into a stable sample

6. V. Half-life of an artifact containing Carbon-14
Half-life number
Fraction of C14 left
Age of artifact 1
1/2
5,730 2
1/4
11,460 3
1/8
17,190 4
1/16
22,920

7. Parent to daughter material
VI. Radiometric Dating – Determining the absolute age of an artifact by comparing the ratios of parent material and daughter material
Parent to daughter material
Unstable to stable
Half Life Time
Uranium-238 to Lead-206
4.5 billion years
Potassium-40 to Argon-40
1.3 billion years
Carbon-14 to Nitrogen-14
5,730 years

8. MICHIGAN’S STATE FOSSIL
ICEMAN
CABON 14
Dating is only
good for objects
that are less than
50,000 years old
MICHIGAN’S STATE FOSSIL
MASTODON

9. Uranium to Lead Method
10 million years and greater

10. Half Life Problems Parent Material AGE OF SPECIMEN
1/8 of Potassium left =
1/2 – 1/4 - 1/8 - 1/16
¼ of Uranium left =
3 x 1.3 = 3.9 Billion
2 x 4.5 = 9 Billion

11. Amount of parent material (half-life # x decay time)
Half-Life Problems
Amount of parent material
Age of artifact
(half-life # x decay time)
1/8 of Carbon-14 left
(How many half-life cycles have occurred?)
3 X 5,730 ys = 17,190 years
grams of Carbon-14. How much would be left after 4 half-life cycles?
20/2 = 10/2=5/2=2.5/2=1.25 grams

12. Radioactive Decay Simulations
Radioactive Decay Simulations