12/3-12/4 Bell ringer... • What is an isotope? • If a sample contains 1000 atoms of Fe with 91.75% Fe-56, 5.85% Fe-54, and 2.40% Fe-57... ✦ What is the atomic mass for the sample? ✦ For the most common isotope how many… ✤ p ? ✤ N ? ✤ e? + 0 - Isotopes and Radiation 0 + Ne-16 Ne-19 Ne-20 Ne-20 Problems with atomic structure... • • Why don’t e- get pulled into the nucleus? Why don’t p+ blow the nucleus apart? Similar systems... • How does these questions compare to our solar system? • • Why don’t the planets get pulled in to the sun? Why doesn’t the sun blow up? Similar systems... Large and small • • Planets don’t get pulled into the sun due to a balance between the outward force of their momentum acting agains the suns gravity e- likewise have outward momentum acting in contrast to the inward pull of their charge attraction Large and small • The nucleus of the atom is held together by what is known as “Strong Force” Strong Force • • • Strong force is a powerful interactive force 0 between the nucleons (p+ & n ) Strong force only acts over very short distances (about the diameter of a p+) Based on gluons, pions, and quarks... What are gluons, pions, and quarks? Don’t ASK!!! Breaking Strong Force • Strong force can be overcome... • • If the nuclei of atoms become too large • Atomic number over 83 If the nuclei has too many or too few n to p+ 0 What happens then? • If strong force is overcome the nucleus begins to break… • • This is radiation! Radiation comes in three primary forms Radiation • • Alpha radiation (α) • Composed of a particle with 2p+ and 2 n 0 Beta radiation (β) • Two forms electron emission (ß-) and positron emission (ß+) ß radiation • • Electron emission (ß-) • Splits a n into a p+ and e0 Positron emission (ß+) • Splits a p+ into a n0 and positron (e+) Summary of radiation Emission (leaving atom) α 4 2 α 4 or 2 He Change in atomic Change in mass # -4amu -2p+ +1p+ -1p+ β- e- 0 (no change) β+ positron (nope) 0 (no change) Gamma radiation! • • • Has a ray nature (no particle is emitted) Does not significantly change mass or charge of nuclei Is represented with an * (Cs-137*)! Radiation • • • U-238 C-14 O-15