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Prelim 1 (Wks 1-6) Significant Figures Counting: 1. All nonzero digits are significant. 2. Zeroes to the left of the first nonzero digit are not significant. 3. Zeroes at the end of a number that includes a decimal point are significant. Addition and Subtraction:- the answer can contain no more decimal places than the least accurate measurement Multiplication and Division:- the answer can contain no more significant figures than the least accurate measurement Scientific Notation Addition and Subtraction numbers converted to same power of 10, coefficients added or subtracted and exponent remains Multiplication coefficients multiplied and exponents added Division coefficients divided, exponent of divisor is subtracted from exponent of number being divided J.J. Thomson cathode ray tubes discovery of electrons Bohrs View there are 2n^2 electrons allowed in a level Modern View orbitals that differ in shape and energy Filling of Orbitals: 1s2s2p3s3p4s3d4p5s 4d5p6s4f (s=2, p=6, d=10, f=14) Trends-Size of atoms decreases as you move from left to right-Size of atoms increases as you move down a group-Reactivity for metals increases as you move down a group-Reactivity for nonmetals decreases as you move down a column Groups: 1A Alkali, 2A Alkali Earths harder, more dense, 7A Halogens diatoms, 8A Noble Gases colorless, not reactive Electromagnetic Radiation: v = C , E=hv- = wavelength, v = frequency, C = speed of light-As decreases, v increases, E increases-As increases, v decreases, E decreases-Troposphere Tropopause (10 km) Stratosphere (Ozone) Mesosphere (temp decreases as you go higher in the troposphere, and then increases as you proceed through the stratosphere)- Anthropogenic pollution attributable to human activity- Clean Air Act (1990) regulates particulates, ozone, CO, nitrogen and sulfur oxides, ozone-depleting chemicals (freons)- Acid Rain H 2 SO 4 (sulfuric acid) acidifies soil and ground water- Thermal Inversion polluted cool air cant rise above warm air Photochemical Smog formed by action of sunlight on photoreactive pollutants in the air Photodissociation of nitrogen dioxide: NO 2 NO + O, O 2 + O O 3 (NO and NO2 are both pollutants)-RO 2 , NO 2 and aldehydes are in smog- Incomplete combustion insufficient oxygen creates CO Solutions to Smog and Ozone-Scrub sulfur dioxide from coal emissions, cars with better mileage, electric or hydrogen, fuel cells, catalytic converters (NO X to N 2 ), minimize volatile organic compounds- Rainout pollutants in air removed by natural precipitation-Because a double bond is stronger than a 1.5 bond and requires more energy to break, oxygen molecules absorb higher-energy UV radiation (UV-C) ozone absorbs lower energy (UV-B) therefore, ozone is more reactive toward UV light than is oxygen.... View Full Document