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Unformatted text preview: Forensic Study Guide 2 03/03/2008 22:12:00 Chapter 6 3/4 of earths crust composed of oxygen and silicon Inorganics do not contain Carbon o Physical Evidence at Crime Scenes (Iron Steel etc.) o Chemical Analysis- trace elements (found in small quantities) The Emission Spectrum of Elements o Elements selectively absorb and emit light. Emission spectroscopy Atomic absorption spectrophotometry Emission Spectrum Light Emitted from a source and separated (by prism) into its component colors or frequencies. Sometimes this produces a continuous spectrum Other times it produces a line spectrum Linespectrums are like an elements fingerprint Excite the element-) Fingerprint Atomic Absorption Elements absorb the same frequencies of light when vaporized The Origin of Emission and Absorption Spectra o Electrons dont weigh much o Atomic Number = The number of protons in the nucleus of an atom. Each element has its own unique atomic number. o Electron Orbitals: The path of electrons as they move around the nuclei of atoms; each orbital is associated with a particular electronic energy level. o Excited State: when electrons get pushed into higher orbitals/ energy levels o Atoms absorb a definite amount of energy o E=hf o F= frequency, H= Placks constant Neutron Activation Analysis o Atomic mass: The sum of the number of protons and neutrons in the nucleus of an atom o Isotope: an atom differing from another atom of the same element in the number of neutrons in the nucleus o Radioactivity: The particle and or gamma-ray radiation emitted by the unstable nucleus of some isotopes o Radioactivity is actively composed of three types of radiation Alpha Rays: Composed of Helium minus its orbiting electrons. Positively Charged...
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- Spring '08