Radio-Active Dating

Radio-Active Dating
HALF LIFE
Recap of Atoms

Parts of an atom


Nucleus (middle of atom)

PROTONS – positive charge

NEUTRONS – no charge
ELECTRONS (outside
nucleus)

Negative charge
Mass Number & Isotopes

Protons & Neutrons have
a mass of 1 each


Mass number =
protons + neutrons
Some elements have
atoms that have a
different number of
neutrons


ISOTOPES
This changes their mass
Radio-active Decay

Isotopes that have
unstable nuceli undergo
radio-active decay


Radioactive isotopes
This means they release
particles or radiant
energy or BOTH
Half-Life

TIME it takes for ½ the
amount of a radioactive
isotope to decay

Many half-lives are
known and can be
seconds to thousands of
years
Carbon Isotopes

Our body has lots of
carbon in it



Mostly Carbon-12
Some Carbon-14
Carbon-14 has a half-life
of 5,715 years
Try it out

If our sample starts with 100 sample size of
carbon-14 and it now has 25, how many half
lives have gone by? How many years old is the
sample?
2 half lives
 11,430 years
