Based on the number of protons and neutrons, an atom can be stable or unstable. Generally, small atoms require an equal number of p & n for stability, larger atoms require more neutrons. Natural Radioactivity To obtain a more stable state, unstable nuclei disproportionate and emit high energy particles and/or electromagnetic radiation (photons) spontaneously. radioactivityradioactive. The name for this process is radioactivity and the substances undergoing such, are said to be radioactive. radioactiveStable Alpha Beta Gamma

Radiation strikes molecules in its path unstable particles e - s may be knocked away, forming unstable particles (ions, radicals) ionizing radiation :. Called ionizing radiation These can cause undesirable chem. reactions which may lead to malignant tumors, leukemia, anemia, or genetic mutations. Biological effect of radiation

Nuclear Reactions All nuclear equations show a balance on mass number & atomic number between the reactants and products: 14 6 Po  He 4 2 ? ? ? + Mass number Atomic number

5 ► 4 He, helium nucleus, contains 2 protons and 2 neutrons ► most ionizing, but least penetrating

60m Co, for example, is produced by the electron emission of 60 Fe.

Technetium (Tc-99m) is a gamma emitter. It can be injected intravenously as a solution of sodium pertechnatate, NaTcO4. Gamma rays emitted by the technetium are detected to produce a scintigram. whole-body bone scintigrams obtained in an adult demonstrate normal anatomy. Extensive osseous metastases from lung carcinoma. The most widely used radioisotope for medical diagnostics.

99 n  p + e- Turns a neutron into a proton: n  p + e- β particle is a high energy electron

Radioactive Iodine ( I-131) therapy is a treatment for an overactive thyroid, a condition called hyperthyroidism. I Xe  + e The radioactive iodine that is not taken up by your thyroid is rapidly eliminated through body fluids such as urine, feces, saliva, and perspiration. Radioiodine is collected by the thyroid gland. The radiation given off by this form of iodine decreases the function of the thyroid cells and inhibits their ability to grow. This is the desired medical effect of this treatment. Some of the other tissues in your body will receive some incidental radiation. This small amount of radiation has NOT been shown to produce any adverse effect.  emissions  emissions 89.9% 7.3% I Xe Xe * 90 %10 %

11 p  n + e+ ► Turns a proton into a neutron: p  n + e+  positron has a charge of +1 and negligible mass ► Antimatter, anti-electron Positron Emission

Positron emission tomography (PET) The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. Fludeoxyglucose is a radiopharmaceutical used in the medical imaging a glucose analog, with the positron-emitting radioactive isotope fluorine-18 substituted for the normal hydroxyl group at the 2' position in the glucose molecule.

PET scan Positron emission tomography

14 occurs when an inner orbital electron is pulled into the nucleus no particle emission, but atom changes proton combines with the electron to make a neutron Electron Capture p + e - → n

15 1. What type of shielding is required for gamma radiation?a. Glovesb. paper and clothing c. lead or concreted. Lab coat and shoes 2. The damaging effects of radiation are due to?a. Production of poisonb. Generation of isotopes c. Generation of radicalsd. Production of new isotopes Practice 3. Write the Nuclear Equation for the Positron Emission From K Write the nuclear equation for the beta decay of cobalt Write a nuclear equation for the electron capture by Be-7

The half-life of a radioisotope is the time for the radiation level to decrease to one-half of the original value. Half-life of a radioisotope Radioisotopes that are naturally occurring tend to have long half-lives used in nuclear medicine have short half-lives

To solve a problem using t 1/2 half-life as a conversion factor 1.Find the number of half-lives within a time period by using the half-life as a conversion factor : time elapsed (days) x1 half-life = number of half-lives 8.0 days 2. Reduce the starting amount of sample by ½ for every half-life. If you find that 2 half-lives elapsed: Starting amount x1 x 1 = amount remaining 2 Example: Phosphorus-32, a radioisotope used in the treatment of leukemia, has a half-life of 14 days. If a sample contains 8.0 g of phosphorus-32, how many grams of phosphorus-32 remain after 42 days? half-life as a conversion factor 1.Find the number of half-lives within a time period by using the half-life as a conversion factor : 42 days x1 half-life = 3 half-lives 14 days 2. Reduce the starting amount of sample by ½ for every half-life. If you find that 2 half-lives elapsed: 8.0 g x 1 x 1 x 1 = 1.0 g 2 2 2

18 6. ) F-18, which has a half-life of 110 min, is used in PET scans. If 100 mg of F-18 is shipped at 8:00 am, how many mg of the radioisotope are still active if the sample arrives at the radiology laboratory at 1:30 pm? a) 50 mgb) 25 mgc) 12.5 mg 7. Phosphorus-32, a radioisotope used in the treatment of leukemia, has a half-life of 14 days. If a sample contains 8.0 g of phosphorus-32, how many grams of phosphorus-32 remain after 42 days?