1. How can we explain absolute dating?

2. ?

3. Elements Ex: Carbon (C), Helium (He)
Exist in varieties called Isotopes
Isotopes differ slightly in mass
Ex: Carbon-14 and Carbon-12

4. Radioactive Decay Unstable isotopes are radioactive
Emit particles and energy through radioactive decay

6. Carbon-14  Nitrogen-14
Uranium-238  Lead-206
The ability of radioactive elements to decay into different elements
This decay continues until stable isotope emerges

8. Carbon-14 The most useful element in dating organic material
Ex: plants and animals

9. Half-Life Time required for half the atoms in a sample to decay
Independent of mass, temperature, and pressure

10. Carbon -14 video How do scientists use carbon 14 for dating?
Does the carbon-12 in organisms ever change?

11. Carbon - 14 What is the half-life of carbon-14? 5,700 years
Predict what ages carbon-14 would be best for
Less than 50,000 years

13. You have 100 g of a substance that has a half-life of 1 hour
Time (hours)
Mass
# of half-lives
Amount of substance left
100 g 1
50 g
1/2 2
25 g
1/4 3
12.5 g
1/8 4
6.25 g
1/16

14. Percent of Carbon -14 remaining
Radioactive Decay
120
100
Percent of Carbon -14 remaining 80 60 40 20 1 2 3 4 5 6
Number of Half-Lives

15. A fossil you found has equal amounts of C-14 and N-14
A fossil you found has equal amounts of C-14 and N-14. How many half-lives have passed? How much time?
C-14  N-14
In 1 half-life, half of the C-14 would be N-14.
According to the ESRT, 1 half life of C-14 is 5.7 x 103 years, or 5700 years.