If you found a fossil with 20.625 atoms of
Carbon14 and 309.375 atoms of Carbon
12, and the half life of Carbon 14 is
5,730years, How old is your fossil?
Ammonite
Step #1 Set up a table like this.
Parent
Daughter
Total
Half Lives
Step #2 Add the two types of atoms found
to determine the total number of atoms.
Carbon 12 +
Carbon14
Total Atoms
309.375
20.625
330
Step #3 Fill in the number of total atoms
and the parent and daughter atoms on
the first line of the chart to show, no
decay, zero half lives.
Parent
330
Daughter
0
Total
330
Half Lives
0
Step #4. Cut the Parent atoms in half
Step #5. Take the total number of atoms
and subtract the parent # of atoms to
get the daughter # of atoms.
Parent
330
Daughter
165
0
165
Total
330
Half Lives
0
330
1
* Note the total number of atoms, never changes.
Step #6 This indicates the 1st half life.
Step # 7 Continue this process until you
find the same number of atoms that were
in your fossil.
Parent
Daughter
330
0
Total
330
165
165 330
82.5
247.5 330
41.25 288.75 330
20.625 309.375 330
330
330
Half Lives
0
1
2
3
4
5
6
Step #8 Note how many half lives it took to
get to the original # of atoms.
Step #9 Multiply the number of half
lives to the original half life of that
type of atom.
If you found a fossil with 20.625 atoms of
Carbon14 and 309.375 atoms of Carbon
12, and the half life of Carbon 14 is 5,730
years, How old is your fossil?
5,730
X
4
Ammonite
22,920 Years
Step #10 Be sure to label your answer.
If you found a fossil with 20.625 atoms of Carbon14
and 309.375 atoms of Carbon 12, and the half life of
Carbon 14 is 5,730years, How old is your fossil?