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Isotopes

Isotopes. Isotopes are forms of the same element but with different #s of neutrons ex. All forms of Carbon still have same atomic # (protons) BUT the # of neutrons can differ C 12 C 13 C 14 6p 6p 6p +6n +7n +8n. Mass Number, Atomic Mass and Atomic Number.

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Isotopes

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  1. Isotopes Isotopes are forms of the same element but with different #s of neutrons ex. All forms of Carbon still have same atomic # (protons) BUT the # of neutrons can differ C12 C13 C14 6p 6p6p +6n +7n +8n

  2. Mass Number, Atomic Mass and Atomic Number Mass Number: # of protons and neutrons. It’s a whole number (12 for Carbon) Atomic Mass: -average mass of the element’s isotopes. It’s a decimal Atomic # (# of protons) is 6

  3. Some Isotopes are Radioactive! Radioactivity- decay of an unstable , high energy atomic nucleus which releases radiation. Radioisotope –An isotope of an element that is radioactive

  4. So how does it work? • Parent nuclide (element)- unstable, higher energy element that decays into another nuclide • Daughter nuclide- stable product that results from this decay Ex. C14 (parent) decays into N14 (daughter)

  5. Discovering Radiation Henri Becquerel 1903 Nobel Prize for physics

  6. http://web.stteresa.edu.hk/~kfyuen/lesson09034.jpg

  7. Types of radiation • Alpha rays (α) Click -easily blocked by clothing, paper, etc. • Beta rays (β)- Nuclear decay by emission of an electronclick -can be stopped by thick wood; used in radiation therapy to kill cancer cells • Gamma rays (γ)- emission of a high energy photon from the nucleus (like an X-ray) click -are a health hazard; maybe blocked by 6 in of cement

  8. Half-life- time it takes for half of the atoms in a radioactive isotope to decay • Each isotope has its own HL -half-life of 238U is 4.5 billion years -half-life of 14C is 5730 years -half-life of 85Kr is 10.76 years Decay continues until a stable, non-radioactive product is formed

  9. Half Life

  10. Half life - a geologic clock

  11. Ex. 210Bismuth Has a half-life of 5 days

  12. Telling time by absolute age Carbon-14 to Nitrogen 14 in ~5700 years found in any living thing Uranium-235 to lead 207 in 700 million years Potassium-40 to Argon-40 in 1.3 billion years found in the mineral feldspar Uranium-238 to lead 206 in 4.5 billion years Thorium 232 to Lead 208 in 14 billion years.

  13. More nuclear reactions…. • Nuclear fission- atom’s nucleus splits into smaller parts; done by firing a neutron at the nucleus demo

  14. Nuclear fusion- 2 or more elements fuse together to from a larger element and release energy in the process (ex. the sun) demo

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