Question

Q1. Carbon-14 – or 14C – is a radioactive isotope of carbon with
a half-life of 5,730 years. It decays into nitrogen-14 – or 14N – ,
which is a stable isotope of nitrogen.

(a) Which of the three nuclear decay processes describes the decay?
Explain. (Hint: You can get the atomic number of carbon and
nitrogen from a periodic table.)

(b) Write down the equation for the decay.

(c) What is the decay constant for 14C?

All isotopes of carbon can be found in any living organism. The
carbon is taken up by eating and breathing. After the organism dies
no more carbon will be replenished and 14C still decays. By
measuring the remaining 14C, when the organism died can be
determined.

(d) An archaeologist has found bones from an animal that have 30%
of 14C compared to its living form. How old is the animal
body?

(e) What would be the percentage of 14C if the animal body was
25,000 years old?

(f) This method of radiocarbon dating can only be used for
relatively young fossils (up to 50,000 years old). Why is that?

Answer #1

Carbon 14 is a radioactive isotope of carbon, the most common
isotope of carbon being carbon 12. Carbon 14 is created when cosmic
ray bombardment changes nitrogen 14 to carbon 14 in the upper
atmosphere. The resulting carbon 14 combines with atmospheric
oxygen to form radioactive carbon dioxide, which is incorporated
into plants by photosynthesis. Animals acquire carbon 14 by eating
plants. When an animal or plant dies, it ceases to take on carbon
14, and the amount of isotope...

The radioactive isotope 14C is produced in the earth’s
atmosphere by bombardment of nitrogen by cosmic rays. The 14C
enters living organisms, where the ratio of 14C to 12C is the same
as in the atmosphere, about . After 1.20×10―12an organism dies, the
14C decays with a half-life of 5730 years. The mass of a neutral
12C atom is 1.993kg.×10―26
(a) A tapestry is determined by mas spectroscopy to contain a
ratio of 14C to 12C of . How old...

The isotope 146C has a half-life of 5,730
years. If a fossil is found to contain 1/64th the amount
of carbon-14 as is typically found in a living plant or animal, how
old is the fossil?

Background:
Excavations at Stonehenge uncovered a number of unshed antlers,
antler tines, and animal bones. Carbon-14 dating methods were used
to estimate the ages of the Stonehenge artifacts. Carbon-14 is one
of three carbon isotopes found in Earth’s atmosphere. Carbon-12
makes up 99% of all of the carbon dioxide in the air. Virtually all
of the remaining 1% is composed of carbon-13. By far, the rarest
form of carbon isotope found in the atmosphere is carbon-14.
The ratio of carbon-14...

Carbon-14 is a radioactive isotope of carbon. It decays into
Nitrogen-14 through beta decay, with a
half-life of 5730 years. By comparing the amount of
radioactive Carbon-14 with the amount of stable
Carbon-12 (the most common isotope of carbon), we can
determine the age of an object.
a) How many protons and neutrons are in Carbon-14?
Carbon-12?
b) How many years will it take for an object to lose 87.5% of
its Carbon-14?
c) If 10000 years have passed, what...

Cosmic rays knock neutrons out of atomic nuclei in the upper
atmosphere. Displaced neutrons hit ordinary nitrogen (14N) at lower
altitudes, converting it into 14C. Unlike common carbon (12C), 14C
is unstable and slowly decays, changing it back to nitrogen and
releasing energy (radioactivity). Living organisms turn atmospheric
carbon into tissue with the same ratio 14C/ 12C as in the
atmosphere (1 in a trillion). How is this process utilized to
determine the age of organic items that are less...

The half-life of a radioactive isotope represents the average
time it would take half of a collection of this type of nucleus to
decay. For example, you start with a sample of 1000 Oxygen-15 (15O)
nuclei, which has a half-life of 122 seconds. After 122 seconds,
half of the 15O nuclei will have decayed into Nitrogen-15 (15N)
nuclei. After another 122s, half of the remaining Oxygen nuclei
will have also decayed, and so on. Suppose you start with 4.00×103
15O...

Background:
Excavations at Stonehenge uncovered a number of unshed antlers,
antler tines, and animal bones. Carbon-14 dating methods were used
to estimate the ages of the Stonehenge artifacts. Carbon-14 is one
of three carbon isotopes found in Earth’s atmosphere. Carbon-12
makes up 99% of all of the carbon dioxide in the air. Virtually all
of the remaining 1% is composed of carbon-13. By far, the rarest
form of carbon isotope found in the atmosphere is carbon-14.
The ratio of carbon-14...

Carbon Dating: All living organisms contain two isotopes (types)
of carbon; carbon-12 ( 12C) and carbon-14 (14C). Carbon-12 is
stable, meaning that its atoms do not decay. Carbon-14 however, is
radioactive or unstable, meaning that an atom of carbon-14 may
decay. It does this by throwing off an electron and thus
transforming itself into Nitrogen 14. The ratio of carbon-14 to
carbon-12 is the same for all living organisims, about 1/10, 000.
However, once an organisim dies the carbon-14 begins...

Given the fact that the lifetime of 14C, the
radioactive isotope of carbon, is approximately 8267 years,
calculate how much time would pass before only 81.1% of the initial
amount of the 14C remains. (Note: the lifetime = half
life/ln (2) = half life/0.6931. The half life of 14C is
5730 years.)
Decay Time (in years):

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