Absolute Dating
Chapter 3, Sec.3
Process to find
the approximate
age of rocks or
fossils
Atoms
Smallest part of matter
Made of protons,
neutrons, electrons
Center called the
nucleus
Everything is
made of atoms
Protons,
neutrons in
nucleus
Electrons move
around nucleus
Every element
has a diff. # of
protons
Isotopes
Atoms of the same
element with
different # of
neutrons
Radioactive Decay
Most atoms are
stable
Some are unstable
and breakdown or
decay (radioactive)
High energy particles
are given off
Can damage cells,
organs, etc..
X-rays, gamma rays,
electrons, protons,
neutrons
Decay occurs
at a constant
rate called
half-life
Half-life
The time it takes
for one-half of a
sample to decay
Problem
I start with 10 grams of a
sample
It’s half-life is 20 years
After 20 years, how much
left? 5 grams
After 40 years, how much left
2.5 grams
Some unstable
isotopes decay
into stable
isotopes
3 radioactive dating
methods
Uranium-Lead Method
Potassium-Argon
Method
Carbon-14 Method