Chemistry Exam 3
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57 terms
Terms | Definitions |
|---|---|
 Carotenes | A class of compounds responsible for the color of carrots and fall leaves. |
| Chlorophylls | A class of compounds found in plant leaves that produce their green color. |
| Electric Field | The area around a charged particle where forces are experienced. |
| Electromagnetic Radiation | Radiation that is propagated by the combination of electric and magnetic fields including gamma rays, X-rays, ultraviolet (UV) light, visible light, infrared (IR) light, microwaves, and radio waves. |
| Electronic Relaxation | An electronic transition in which an electron goes form a higher-energy orbit to a lower-energy one. |
| Electronic Transition | When the electrons in an atom or molecule move from one energy state to another. |
| Energy State | The electron configuration of a molecule or atom with electrons in particular orbits and therefore at particular energies. |
| Excited State | An unstable state for an atom or molecule in which energy has been absorbed but not reemitted. |
| Fluorescence | The fast emission of light following electronic excitation. |
| Frequency | For a wave, the number of cycles or rests that pass through a point in one second, usually reported in units of cycles per second or hertz. |
| Gamma Rays | The shortest wavelength and most energetic form of electromagnetic radiation. Each consists of an energetic photon emitted by an atomic nucleus and is represented by the symbol ₀⁰γ |
| Hertz, Heinrich | (1857-1894) German physicist who discovered radio waves in 1888. |
| Infrared (IR) Light | That portion of the electromagnetic spectrum that is immediately adjacent to red light. It is invisible to the human eye. |
| Laser | An acronym for light amplification by stimulated emission of radiation. They produce intense, single-wavelength light. |
| Laser Cavity | In a laser, the lasing medium is placed inside this consisting of two mirrors, one of which is only partially reflecting. |
| Lasing Medium | Laser light is formed by putting electrical or light energy into an element or a compound called the lasing medium. |
| Magnetic Field | The area around a magnet where forces are experienced. |
| Microwave Radiation | The fraction of the electromagnetic spectrum that is between the infrared (IR) region and the radio wave region. It is efficiently absorbed by water molecules and can therefore be used to heat water-containing substances. |
| Phosphorescence | The slow emission of light following electronic excitation. |
| Photodecomposition | The breaking of bonds within molecules due to the absorption of light. |
| Photons | Particles of light. |
| Radio Waves | The longest wavelength and least energetic form of electromagnetic radiation. They are used extensively as a medium for communication and broadcasting. |
| Roentgen, Wilhelm | (1845-1923) A German physicist who discovered X-rays. |
| Spectroscopy | The interaction of light with matter. |
| Ultraviolet (UV) Light | The fraction of the electromagnetic spectrum that is between the visible region and the X-ray region. It is invisible to the human eye. |
| Visible Light | The fraction of the electromagnetic spectrum that is visible to the human eye. The visible region is bracketed by wavelengths of 400 nanometers (nm, violet) and 7800 nm (red) and contains all wavelengths in between. |
| Wavelength | The distance between wave crests, usually reported in units of length such as meters of nanometers. |
| X-rays | The fraction of the electromagnetic spectrum that is between the ultraviolet (UV) region and the gamma ray region. They can penetrate substances that normally block light and are often used in medical diagnosis. |
| Becquerel, Antoine-Henri | (1852-1908) French physicist who accidentally discovered radioactivity while studying X-rays. |
| Critical Mass | The mass of uranium or plutonium required for a nuclear reaction to be self-sustaining. |
| Curie, Marie Sklodowska | (1867-1934) French (Polish-born) chemist who helped understand radioactivity and also discovered two new elements together with her husband Pierre Curie. |
| Curie, Pierre | (1859-1906) French chemist who helped understand radioactivity and also discovered two new elements together with his wife Marie Curie. |
| Einstein, Albert | (1879-1955) Physicist who discovered relativity, contributed to the discovery of quantum mechanics, and persuaded President Roosevelt to start the Manhattan Project. |
| Fermi, Enrico | (1901-1954) Italian physicist who played an important role in the development of nuclear fission. In collaboration with Szilard, he constructed the first nuclear reactor. |
| Fission | The splitting of a heavy atomic nucleus to form lighter ones. |
| Fusion | The combination of light atomic nuclei to form heavier ones. |
| Hahn, Otto | (1879-1968) German chemist credited as one of the discoverers of nuclear fusion. |
| Half-Life | For a radioactive element, the time required for half of the nuclei in a sample to decay. |
| Ionizing Power | The tendency of particular solvent to promote ionization of an uncharged or, less often, charged solution. |
| Mass Defect | The difference between the experimentally measured mass of a nucleus and the sum of the masses of the protons and neutrons contained in the nucleus. |
| Meitner, Lise | (1878-1968) German chemist credited as one of the discoverers of nuclear fusion. |
| Nuclear Binding Energy | The energy that hold a nucleus together. |
| Nuclear Equation | An equation that represents a nuclear reaction. They must be balanced with respect to mass number and atomic number. |
| Oppenheimer, J.R. | (1904-1967) Director of the Manhattan Project, the U.S. endeavor to build the world's first nuclear weapon. |
| Radon | A radioactive gas emitted by the decay of uranium. It is by far the greatest single source of radiation exposure for humans. |
| Rem | The most common unit for measuring human exposure to radiation. |
| Strassmann, Fritz | (1902-1980) Chemist credited as one of the discoverers of nuclear fusion. |
| Szilard, Leo | (1898-1964) American (Hungarian-born) physicist who played an important role in the development of nuclear fission. In collaboration with Fermi, he constructed the first nuclear reactor. |
| Atmosphere | The envelope of gases surrounding the earth or another planet |
| Barometer | Device that measures pressure. |
| Chlorofluorocarbons (CFCs) | A family of compounds containing carbon, chlorine and fluorine. They are implicated in the destruction of ozone and were banned from production in the UNited States in 1996. |
| Ionosphere | The highest section of the atmosphere ranging from altitudes of 80-160 km. |
| Mesosphere | The region of the atmosphere ranging from altitudes of 50-80 km. |
| Nitrogen Fixation | The conversion of nitrogen molecules (N₂) into nitrogen compounds such as ammonia or nitrates that can be absorbed by plants. |
| Pressure | The net force created by the constant pelting of gas molecules against surfaces. |
| Stratosphere | The region of the atmosphere ranging from altitudes of 10-50 km and containing the ozone (O₃) layer. |
| Troposphere | The lowest part of the atmosphere ranging from ground level to altitudes of 10 km (6 mi). |
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