Transcript Document
Absolute Ages of Rocks
Sci. 3.3
Absolute age:
• Age in years
Question 1
Nucleus (center) of atom:
• Protons, + charge
• Neutrons, No charge (Neutral)
• Electrons, - charge outside nucleus
eP
H
eN
P P
e- N
He
Draw these
e-
e-
PN
NPN P
e-
Li
Question 2
2a. Which subatomic particle is not found
in the nucleus? P. n. e
2b. A neutron has a _____ charge. Positive,
negative, no charge
eP
eN
P P
e- N
H
He
1P
2P
e-
PN
NPN P
e-
Number of protons:
• Determines identity of element
e-
Li
3P
Question 3
3a. If a He atom lost a proton, it would
become what element? H, Li, C, O
3b. If a He atom gained a proton, it would
become what kind of atom? H, Li, C, O
Number of neutrons:
• Determines which form (isotope) of element
Carbon 12
Carbon 14
6P
6N
6P
8N
12C
14C
Nitrogen 14
7P
7N
14N
Potassium 40
Sodium 23
19 P
21 N
11 P
12 N
40K
23Na
Argon 40
18 P
22 N
40Ar
Hydrogen 2
Nitrogen 15
1P
1N
7P
8N
2H
15N
Phosphorus 28
15 P
13 N
28P
Question 4
4a. How many neutrons does the
isotope 14C have? 6, 7, 8, 14
4b. How many neutrons does the
isotope 13C have? 6, 7, 8, 13
Some isotopes are unstable
• Radioactive decay
Parent material
14C
Daughter material
14N
e-
Question 5
5a. All carbon atoms have __
protons. 6, 7, 8, 14
5b. All nitrogen atoms have __
protons. 6, 7, 8, 14
Half-life:
• Time it takes for half of atoms to decay
• Ex:14C = 5730 years (235U=700 m.y., 238U=4.5 b.y.)
Question 6
6a. If an organism had 100g of 14C when it
died around 11,500 years ago (2 half-lives),
how much 14C would it have today? 200, 50,
25g, 15g
6b. If an organism had 120g of 14C when it
died around 17,000 years ago (3 half-lives),
how much 14C would it have today? 360, 60,
30g, 15g
Radiometric dating:
• Calculating age based on half-life
• ratio of parent material to daughter material
Question 7
Radiocarbon
dating:
•
•
•
•
For dating dead things
good to 75k years ago
For original remains only
(dinos 65mil )
Shroud of Turin
Question 8
8a. Would radiocarbon dating be useful for
dating the exact age of the earth (~4.6 billion
years)? Y/N
8b. Would radiocarbon dating be useful for
dating a trace fossil that is around 50k years
old? Y/N
Earth’s age
• ~4.5 bil. years
• Oldest rocks ~3.9 bil
Question 9
9a. The earth is approximately how old?
4.5 bil, 4.5 mil, 4.5 thousand
9b. When the earth first formed, its surface:
was molten rock, lacked liquid water, did not
have an atmosphere, all of the above
uniformitarianism:
• Processes that change the earth today, are the same
that changed it in the past
Question 10
10a. The processes that shape the
earth’s surface generally work:
very slowly, very quickly
10b. Which process forms new
elements? uniformitarianism,
superposition, permineralization,
radioactive decay