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