i. transmutation transmutation - the conversion of one element to another element. all nuclear...

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Page 1: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma
Page 2: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

I. Transmutation

• Transmutation - The conversion of one element to another element.

• All nuclear reactions are transmutation reactions except for gamma emission, which does not alter an atom’s atomic number.

Page 3: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

II. Induced Transmutation

• Before 1919, the only way to change the nucleus or cause transmutation was to wait for nature.

• In 1919 Rutherford was the first to induce (cause) transmutation.

• He proved that nuclear reactions can be produced artificially.

• Induced transmutation can occur by bombarding an atom with alpha particles, protons or neutrons.

Page 4: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma
Page 5: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

III. Transuranium Elements

• Elements with atomic number above 92.• All transuranium elements undergo

transmutation• None of the transuranium elements occur in

nature and have been produced through induced transmutation.

Page 6: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

IV. Half-life

• The time required for one-half of a radioisotope’s nuclei to decay into its products

• After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element

• Amount remaining at time T = (initial amt)(1/2)n

where n= number of half-lives• n = total time ÷ time of one half-life

Page 7: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma
Page 8: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

Half-Life Skip count50.0 g 25.0 g 12.5 g 6.25 g 3.125 g ≈3.13 g

1 2 3 4

Practice1. Scientists start with 50.0 g sample of

a radioisotope. How much is left after four half-lives?

Page 9: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

2. Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron 59 is 44.5 days. How much of a 2.000 mg sample will remain after 133.5 days?

(first find out how many half-lives, then skip count)

Page 10: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

Half-Life Skip count2.000 mg 1.000 mg 0.5000 mg 0.2500 mg

1 2 3

133.5 days44.5 days= 3 half-lives

Page 11: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

V. Carbon-14 Dating• Carbon 14 dating is the process of

determining the age of artifacts that were once part of a living organism by measuring the amount of 14C remaining in that artifact

• Carbon-14 is radioactive and undergoes beta decay. It has a half-life of 5730 years.

Page 12: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

Carbon-14• 14C evenly spread in the Earth’s biosphere• Plants incorporate 14C into their structure that

matches the level in the atmosphere.• When an organism dies, 14C declines at a known

rate. (Half-life of C-14 = 5730 years)• Comparing the remaining 14C fraction of a sample

to that expected from atmospheric 14C allows the age of the sample to be estimated.

• Dates carbon-bearing materials up to 62,000 years.

Page 13: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma

Carbon-14 Decay

• Using the graph, about what % of carbon-14 remains after 11, 400 years?

Page 14: I. Transmutation Transmutation - The conversion of one element to another element. All nuclear reactions are transmutation reactions except for gamma