CONCURRENT ENROLLMENT CHEMISTRY CHAPTER 10 CONCURRENT ENROLLMENT CHEMISTRY

RADIOACTIVE NUCLEI Nuclei that undergo spontaneous changes and emit energy in the form of radiation Henri Becquerel- 1896 Radioactive decay Unstable nuclei emit radiation to attain more stable atomic configurations in a process called radioactive decay.

RADITATION Three types of radiation Alpha particles 42α or 42He 2+ Identical to helium nuceli

BETA PARITCLES Beta particles -10β or -10e- Identical to an electron but is produced when a neutron becomes a proton by releasing an electron

GAMMA RAYS Gamma rays have no mass or charge. 00γ Gamma rays are high-energy electromagnetic radiation. Gamma rays almost always accompany alpha and beta radiation. X rays are a form of high-energy electromagnetic radiation emitted from certain materials in an excited state. The ability of radiation to pass through matter is called its penetrating power. Gamma rays are highly penetrating because they have no charge and no mass Learning check page 314

CONTINUED

Except for gamma radiation, radioactive decay involves transmutation, or the conversion of an element into another element. Protons and neutrons are referred to as nucleons. All nucleons remain in the dense nucleus because of the strong nuclear force. The strong nuclear force acts on subatomic particles that are extremely close together and overcomes the electrostatic repulsion among protons.

CONTINUED The area on the graph within which all stable nuclei are found is known as the band of stability The band ends at Pb-208; all elements with atomic numbers greater than 83 are radioactive.

Positron and electron capture Daughter nuclei Learning check page 315 Positron 10e+ This is used in PET scans of the brain Proton changes into a neutron Electron capture Learning checks on pages 315 and 316 Table 10-2 on page 313

Writing and Balancing Nuclear Equations

ISOTOPE HALF-LIFE The time required for one-half the unstable nuclei in a sample to undergo radioactive decay Learning checks 317 and 318 N is the remaining amount. N0 is the initial amount. n is the number of half-lives that have passed. t is the elapsed time and T is the duration of the half-life.

CONTINUED Free radical Radiation sickness Table 10.3 page 319 An electron-deficient particle that is very reactive Radiation sickness Table 10.3 page 319

MEASUREMENTS Curie Becquerel Roentgen Rad Unit of radiation measurement corresponding to 3.7 X 1010 nuclear disintegrations per second Becquerel Unit of radiation measurement corresponding to one nuclear disintegration per second Roentgen A biological unit of radiation measurement used with X rays and gamma rays; the quantity of radiation that generates 2.1 X 109 ion pairs per 1 cm3 of dry air or 1.8 X 1012 ion pairs per 1 g of tissue Rad A biological unit of radiation measurement corresponding to the transfer of 2.1 X 10-3 cal of energy to 1 kg of tissue

CONTINUED Gray Rem Geiger-Müller tube or counter A biological unit of radiation measurement corresponding to the transfer of 1 J of energy to 1 kg of tissue Rem A biological unit of radiation measurement corresponding to the health effect produced by 1 roentgen of gamma or X-ray regardless of the type of radiation involved Geiger-Müller tube or counter A radiation-detection device operating on the principle that ions form when radiation passes through a tube filled with low-pressure gas

MEDICAL USES OR RADIOISOTOPES Tracer A radioisotope used medically because its progress through the body or localization in specific organs can be followed. Tracers should have short half-lives Daughter produced from decaying isotope should be nontoxic Radioisotope should have a long enough half-life to be prepared and administered Radiation given off by the isotope should be penetrating gamma rays, so they can be detected Hot spot Cold spot

CONTINUED Radioisotopes administered internally for therapeutic use should ideally Emit less penetrating alpha or beta radiation to restrict the extent of damage Half-life should be long enough to allow sufficient time for the desired therapy Decay products should be nontoxic and give off little or no radiation Target tissue should concentrate the radioisotope to restrict the radiation damage Table 10.6 page 324

NONMEDICAL USES Radioactive dating Nuclear fission Chain reaction A process for determining the age of artifacts and rocks, based on the amount and half-life of radioisotopes contained in the object Carbon-14 dating uses its half-life of 5600 years Nuclear fission A process in which large nuclei split into smaller, approximately equal-sized nuclei when bombarded by neutrons Chain reaction A nuclear reaction in which the products of one reaction cause a repeat of the reaction to take place. In the case of uranium fission, neutrons from fission reactions cause other fission reaction to occur

CONTINUED Branching chain reaction Critical reaction A reaction in which the products of one reaction cause more than one more reaction to occur Critical reaction A constant-rate chain reaction Supercritical reaction A branching chain reaction Critical mass The minimum amount of fissionable material needed to sustain a critical chain reaction at a constant rate Supercritical mass The minimum amount of fissionable material that must be present to cause a branching chain reaction to occur

LAST PAGE Breeding reactions Thermonuclear reactions Nuclear fusion A nuclear reaction in which isotopes that will not undergo spontaneous fission are changed into isotopes that will Thermonuclear reactions Nuclear fusion reactions that require a very high temperature to start them Nuclear fusion A process in which small nuclei combine or fuse to form larger nuclei