1. Half-Life and radiometric dating
Absolute Age
Half-Life and radiometric dating

2. Half-Life
Atoms are the building blocks of all matter.

3. Half-Life Atoms have 3 small parts: protons (positive charge)
neutrons (no charge)
electrons (negative charge)

4. Half-Life
An element is defined by how many protons it has (this is its atomic number).
Carbon’s atomic number is 6.
It has 6 protons.

5. Half-Life
Isotope: atoms of an element that have the same number of protons, but a different number of neutrons.

6. Half-Life Normal carbon is called carbon-12 and it has 6 neutrons.
Carbon isotopes:
carbon-13 has 7 neutrons
carbon-14 has 8 neutrons

7. Atoms and Isotopes

8. Half-Life Isotopes can be stable or unstable.
When they are unstable, they are called radioactive, and they can’t keep themselves together – they decay.
Radioactive Decay

9. Half-Life
Radioactive decay happens when an unstable nucleus changes into another kind of nucleus by releasing particles and energy.

10. Half-Life The isotope that decays is called the parent isotope.
The stable element that forms is called the daughter isotope.
Parent
Daughter

11. Half-Life
Radioactive decay is a natural clock that scientists can use to find the ages of rocks.

12. Half-Life
Parent isotopes decay into daughter isotopes at a constant rate (the decay rate).

13. Half-Life
The half-life of an element is the length of time it takes for half of the parent isotope to decay.

14. Half-Life

15. Half-Life
The half-life of Carbon-14 is years.

16. Half-Life Half-life of the carbon-14 isotope: 1/2 left after 5730
years
1/4 left
after
another
5730
years
1/8 left
after
another
5730
years
1/1 at
start

17. Half-Life

18. Half-Life
Comparing the amount of parent to daughter material determines the number of half- lives the material has been through.

19. The Age of Earth
The oldest rocks on Earth are estimated to be 4.0 to 4.4 billion years old.

20. The Age of Earth
The ages of meteorites recently collected in Antarctica are billion years old.

21. The Age of Earth
The ages of rocks collected from the moon are about 4.6 billion years old.

22. The Age of Earth
Earth is approximately 4.6 billion years old.