Solve: The periodic table shows that radium has an atomic number of 88. The complete chemical symbol for radium-226 is therefore . An alpha particle is a helium-4 nucleus, and so its symbol is (sometimes written as ). The alpha particle is a product of the nuclear reaction, and so the equation is of the form where A is the mass number of the product nucleus and Z is its atomic number. Mass numbers and atomic numbers must balance, so And Hence, Again, from the periodic table, the element with Z = 86 is radon (Rn). The product, therefore, is Rn, and the nuclear equation is
Radiation Penetration Addition of an electron to a proton in the nucleus is known as electron capture or K- capture . – The result of this process is that a proton is transformed into a neutron. Property Alpha ( α ) Particle Beta ( β ) Particle Gamma ( γ ) Ray Travel Distance in Air 2 to 4 cm 200 to 300 cm 500 m Tissue Depth 0.05 mm 4 to 5 mm 50 cm or more shielding Paper, clothing Heavy clothing, lab coats, gloves Lead, thick concrete Typical source Radium-226 Carbon-14 Technetium-99m
Bombardment We can combine two stable nuclei to form an unstable, radioactive nucleus. • All elements that have an atomic number greater than 92 have been produced by bombardment.
Bombardment when californium-249 is bombarded with nitrogen-15, the radioactive element dubnium-260 and four neutrons are produced
Measuring Radiation The curie ( Ci) – original unit of activity – defined as the number of disintegrations that occurs in 1 s for 1 g of radium, which is equal to 3.7 × 10 10 disintegrations/s. – SI unit of radiation activity is the becquerel (Bq) , which is 1 disintegration/s.
Measuring Radiation • The rad (radiation absorbed dose) – measures the amount of radiation absorbed by a gram of material such as body tissue. – The SI unit for absorbed dose is the gray ( Gy) • Joules of energy absorbed by 1 kg of body tissue. – The gray is equal to 100 rad.
Measuring Radiation • rem (radiation equivalent in humans) – measures the biological effects of different kinds of radiation. For example, although alpha particles do not penetrate the skin, if they should enter the body by some other route, they can cause extensive damage within a short distance in tissue. High-energy radiation, that travel into tissue, cause more damage. • Often, the measurement for an equivalent dose will be in units of millirems (mrem). One rem is equal to 1000 mrem • The SI unit is the sievert (Sv) . One sievert is equal to 100 rem.
Measuring Radiation • rem (radiation equivalent in humans) – To determine the equivalent dose or rem dose, the absorbed dose (rad) is multiplied by a factor that adjusts for biological damage caused by a particular form of radiation. For beta and gamma radiation the factor is 1, so the biological damage in rems is the same as the absorbed radiation (rad). For high-energy protons and neutrons, the factor is about 10, and for alpha particles it is 20.