1. 7.2 Half Life
Half Life: the constant rate at which radioactive isotopes naturally decay.
This rate refers to the time it takes for half of the nuclei of a sample to decay.
With every half life, half of the remaining nuclei decays until there is no more.

2. Carbon Dating (C-14) Carbon has 3 isotopes: C-12, C-13 and C-14
All organisms contain carbon. When an organism is alive the ratio of C-12 to C-14 is equal…but when an organism dies C-12 remains constant but C-14 decays without being replaced.
Overtime the ratio of C-14 and C-12 decreases
This ratio is used to estimate the age of an organisms remains.
Radiocarbon dating: process that determines the age of an organism by determining the C-14 remaining.
Only organisms that have lived within the last 50,000 yrs

3. Carbon Dating

4. Decay Curves
A curved line on a graph that shows the rate at which radioisotopes decay
Regardless of the radioisotope graphed all decay curves have a similar shape
Difference: half life length will vary, every isotope has its own half life which can range from 1 second to an hour to thousands of years etc.

5. Decay Curve

6. Potassium-40 Clock
Parent Isotope: the isotope that undergoes radioactive decay
Daughter Isotope: the stable product of the radioactive decay.
Isotope pairs can be used in radioactive dating. Notice how the dating ranges differ based on half-life.
See Table 7.6 on pg 307
Notice how the red and blue curves intersect at the 1st f half life only 