Quiz: Half Life
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27 Terms
Most atoms are
stable
Carbon-12 will be Carbon-12
forever
Oxygen-16 will be Oxygen-16
forever
Some atoms are
unstable
They break down or “decay” into
other atoms
Carbon-14 and Uranium 238 is
radioactive
Carbon-14 decays into
Nitrogen-14
Uranium 238 decays into
Lead-206
When an radioactive element decays,
it changes into a stable Daughter Product
Carbon-14 is the
radioactive element
Uranium-238 is a
Lead-206 is the
stable daughter product
The length of time it takes half of the atoms of a radioactive substance to decay into the daughter product is called the
Half life
Half life is the lifetime of half of the
radioactive atoms in a rock
The half-life NEVER changes for an element no matter
how many atoms you start with.
0: 16 half radioactive atoms
0 daughter products atoms
1 half life: 8 radioactive atoms
8 daughter product atoms
2 half-lives: 4 radioactive atoms
12 daughter product atoms
3 half lives: 2 radioactive atoms
14 daughter products atoms
After each half-life, we only have 1/2 of the atoms of the radioactive element left no mater how many we start with:
Beginning = 100 grams
After 1 half-life = 50 grams
After 2 half-lives = 25 grams
After 3 half lives = 12.5 grams
Every half-life,
we have more atoms of the daughter product
Every half-life, we have more atoms of the daughter product
radioactive stable
atoms atoms
Beginning = 160 0
After 1 half-life = 80 80
After 2 half-lives = 40 120
After 3 half lives = 20 140
Carbon-14 has a half-life of 5730 years
0 years = 100 grams
After 5730 years = 50 grams
After 11460 years = 25 grams
After 17190 years = 12.5 grams
Uranium-238 has a half-life of 4.5 billion years:
0 years = 100 grams
After 4.5 billion years = 50 grams
After 9 billion years = 25 grams
After 13.5 billion years = 12.5 grams
To tell the age of a rock we need to know 3 things
The number of atoms of the radioactive parent element in the rock
The number of atoms of the stable daughter product in the rock
The length of the half-life of the radioactive element