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Transmutation of Elements

Transmutation of Elements. In 1915 Rutherford realized that elements can be artificially created by bombarding on particles with another particle in a particle accelerator (cyclotron). n. or. 12. Cf + C . Rf + 4. 249. 257. 1. 6. 98. 104. 0. n. 18. Cf + O . Sg + 4.

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Transmutation of Elements

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  1. Transmutation of Elements • In 1915 Rutherford realized that elements can be artificially created by bombarding on particles with anotherparticle in a particle accelerator (cyclotron). n or 12 Cf + C  Rf + 4 249 257 1 6 98 104 0 n 18 Cf + O  Sg + 4 249 263 1 8 98 106 0

  2. Transmutation Practice • Theoretically, you could produce a Au-199 atom if you can effectively collide Re-190 with what other isotope? • If you bombard Au-197 with Co-110, what element would be produced if 4 neutrons resulted?

  3. Half-life Concept • Definition - The time it takes for half a sample of radioactive isotope to decay. • Unlike chemical reactions, the decay of an element is not influenced by pressure or temperature. • Decay is based upon the strong nuclear force being able to overcome the electrostatic repulsion of all the protons in the nucleus. • Nucleus wants to keep that magic 1.5:1 ratio.

  4. Common Elements with Useful Half-life Times • Potassium-40 has a half-life of 1.28 billion years. • Good for dating ancient rocks and minerals • Carbon-14 has a half-life of 5,715 years. • Can only be used to date things that were living. • Iodine-131 has a half-life of about 8 days. • Good for medical tests, specifically related to thyroids.

  5. Half-life Examples Start with 100 grams of a radioactive sample. 1 half-life goes by…. We now only have 50 grams of the radioactive sample. After one more half-life goes by…. We now only have 25 grams of the radioactive sample.

  6. Half - life w/o a formula 1st step, find out the total mass of the original sample 2nd step, find out the length of the half-life 3rd step, cut the total mass in half until you reach your desired time or mass remaining

  7. Half-life Question • Rutherford purchased 25 grams of Cesium-137. If the half-life of Cs-137 is 30 years, how much sample will be remaining after 60 years? How many half-lives? 60/30 = 2. SO… After 1 half-life: (1/2)*(25g) = 12.5g of Cs left After 1 more half-life: (1/2)*(12.5g) = 6.25 g of Cs left

  8. Half-life Questions (cont.) • There is a shortcut… • Formula: r = m (.5)h • r is the amount of sample remaining • m is the mass of the sample at the start • h is the number of half-lives - this can be found by taking: length of time/length of half-life

  9. Half-life Question with Formula… Rutherford purchased 25 grams of Cesium-137. If the half-life of Cs-137 is 30 years, how much sample will be remaining after 60 years? r = 25g (.5)2 r = 6.25 g

  10. Another Half-life Question • A substance has a half-life of 3,000 years. How much of a 40 gram sample will be left after 12,000 years? r = 40g (.5)4 r = 2.5 g

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