2. DNA molecule EXAMPLE: CARBON AND ITS ISOTOPES CHEMICAL ELEMENTS & ISOTOPES CARBON = C (COAL, DIAMOND) C-22 6P+16N T½=9ms M=22.056 C-9 6P+3N T½=127ms M=9.031 C-11 6P+5N T½=20min M=11.0114 C-14 6P+8N T½=5715y (from N-14 + n) (~4kBq in 70kg man, none in coal) M=14.0032 C-18 6P+12N T½=0.09s M=18.0268 C-12 6P+6N STABLE – 18% of body mass M=12.000000 C-12 6P+6N STABLE – 18% of body mass M=12.000000 C-13 6P+7N STABLE – 1.1% of C M=13.0034 C-15 6P+9N T½=2.45s M=15.0106 Question : Where does nuclear energy come from ? Clue : E = mc 2 Answer : The slight excess of mass of the less stable isotopes is converted to energy when isotopes are converted from less stable to more stable ones.

3. CARBON ISOTOPES 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 BORON ISOTOPES NITROGEN ISOTOPES CARBON ISOTOPES BORON NITROGEN CARBON OXYGEN BERYLLIUM BORON NITROGEN CARBON OXYGEN BERYLLIUM LITHIUM HELIUM HYDROGEN neutron FLUORINE NEON BORON NITROGEN CARBON OXYGEN BERYLLIUM LITHIUM HELIUM HYDROGEN neutron FLUORINE NEON SODIUM MAGNESIUM ALUMINIUM SILICON PHOSPHORUS SULFUR CHLORINE ARGON POTASSIUM CALCIUM ALSO CALLED “CHART OF THE NUCLIDES” TABLE OF ISOTOPES CARBON - 12

4. H He Li Be B C F O N Si Al Mg Na Ne Cl S P Ar Ca K ALSO CALLED “CHART OF THE NUCLIDES” TABLE OF ISOTOPES Mg-35 (T½=0.07 sec) Na-35 (T½=1.5 msec) Al-35 (T½=0.03 sec) Si-35 (T½=0.9 sec) P-35 (T½=47 sec) S-35 (T½=87.2 d) Cl-35 (stable) Question : What is more radioactive ? A) an isotope with a long half-life ? or B) an isotope with a short half-life ? (assume you have 1 kg of each) Clue # 1: Think of nuclear radiation as a form of light (high energy form of light) Clue # 2: Think of radioactive isotopes as a store of energy (like an electric battery) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1 2 3 6 5 4 10 9 8 7 15 14 13 12 11 19 18 17 16 20

5. Clue # 3 Little radiation for weeks Powerful radiation for…. ….one minute ? Identical car batteries – both charged to full Answer : The isotope with a short half-life is more radioactive because all its energy is radiated away quickly !!

6. CHART OF THE NUCLIDES – EXCESS MASS CHEMICAL ELEMENTS & ISOTOPES RADIOACTIVE DECAY “VALLEY OF STABILITY” Na-35 (T½=1.5 msec) Cl-35 (stable) Skip next

7. H He Li Be B C F O N Si Al Mg Na Ne Cl S P Ar Ca K 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1 2 3 6 5 4 10 9 8 7 15 14 13 12 11 19 18 17 16 20 ALSO CALLED “CHART OF THE NUCLIDES” TABLE OF ISOTOPES URANIUM-235 ( U-235 ) comprises 0.71% of natural uranium (99.28% U-238) (0.006% U-234) Example : U-235 + n°  Y-96 + I-138 + 2n° (Uranium 235) (Yittrium 96) (Iodine 138) C-12 IRON-56 ( Fe-56 ) Ba-138 (stable) Cs-138 (T½=32.2 min) Xe-138 (T½=14.1 min) I-138 (T½=6.5 sec) Mo-96 (stable) Nb-96 (T½=23.4 hr) Zr-96 (T½=2x10 19 y) Y-96 (T½=6.2 sec)

8. CHART OF THE NUCLIDES – EXCESS MASS TABLE OF ISOTOPES IN 3-D U-235 U-235 + n°  Y-96 + I-138 + 2n° (Uranium 235) (Yittrium 96) (Iodine 138) I-138 (T½=6.5 sec) Y-96 (T½=6.2 sec) Mo-96 (stable) Ba-138 (stable)