Chem 1314 week 2 notes
Chem 1314 week 2 notes Chem 1314
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This 3 page Class Notes was uploaded by Morgan Walker on Saturday January 23, 2016. The Class Notes belongs to Chem 1314 at Oklahoma State University taught by Dr. Jimmie Weaver in Winter 2016. Since its upload, it has received 67 views. For similar materials see General Chemistry in Chemistry at Oklahoma State University.
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Date Created: 01/23/16
Chapter 2 Atoms and Elements Law of Conservation of Mass- mass is neither created or destroyed, just reconfigured Law of Definite Proportion- a pure compound always has the exact same proportions of elements by mass Water will always have 11.2% H and 88.8% O by mass o 2 hydrogen and 1 oxygen Law of Multiple Proportions- elements may combine in more than one ratio but will no longer be the same compound 2 N + O -> N2O dinotrogen monoxide (laughing gas) N + 2O -> NO 2 nitrogen dioxide (photochemical smog) Dalton’s Atomic Theory 1. Elements are composed of atoms 2. All atoms of an element are the same but the atoms in a different element are different a. Hydrogen atoms are different from gold atoms 3. Compounds are made of atoms from more than one element 4. Chemical reaction only separates, combines or rearranges atoms. Does not destroy or create them J.J Thompson’s Experiment (pg 51 in book) Thompson performed experiments to probe the properties of a cathode ray. He applied a high electrical voltage in-between two electrodes at either end of the tube. He found that the cathode rays, beams of particles, moved from negatively charged electrode (cathode) to positive (anode). He found that the particles in the ray have certain properties: 1. Travel in a straight line 2. Independent from the composition of the material from which they come from 3. Carry a negative electrical charge He then measured the charge-to-mass ratio of the ray particles by using a magnetic field to deflect them. 8 The value was -1.76 X 10 coulombs. Lightest know atom. He discovered that the electron was a negatively charged and low mass particle that is present in all atoms. Millikan’s Oil Drop Experiment (pg 52 in book) He sprayed oil into fine droplets using the atomizer and the atoms fell due to the influence of gravity through a small hole into the lower portion where he viewed them with a light source and a microscope. While the droplets fell they gained electrons from ionizing radiation in the air of the chamber which gave the droplets a negative charge and Millikan was able to create an electric field between a positively charged plate (top) and a negatively charged plate (bottom). He then measured the strength of the electric field required to stop the particles then using their radii and density he found their masses he found the charge of the particles. -19 The charge was -1.60 X 10 C Structure of the Atom J.J Thompson’s Plum Pudding atomic model Suggested that the negatively charged electrons were held inside a positively charged sphere Would look like a blueberry muffin o Blueberries were electrons, muffin was the positively charged space Rutherford’s Gold Foil experiment Proved Thompson’s experiment wrong Shot alpha particles through a gold sheet and if the sheet really was like a blueberry muffin then the particles would go straight through. some did, some deflected and few bounced back Concluded that matter isn’t as uniform as it seems. Must have large regions of empty space with small regions of very dense matter. Nuclear Theory 1. Most of the mass of the atom and all of its positive charge are located in the small core called the nucleus 2. Most of the atom’s volume is empty space with small negatively charged electrons dispersed throughout 3. The amount of electrons outside the nucleus are equal to the amount of positively charged protons inside the nucleus, atom is electrically neutral. Atomic number, mass number and isotopes Atomic number- number of protons inside the nucleus Mass number- number of protons plus number of neutrons Isotopes- atoms that have the same number of protons and a different number of neutrons Atomic mass unit- exactly one-twelfth the mass of 1 carbon 12 atom Mole One mole will always have the same number of atoms no matter what it weighs 6.022 X 103(Avogadro’s number) Atomic or molecular mass unit g/mol Weighted average ∑ ((fraction of isotope) X mass of isotope)
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