Chemistry 141 Week 3
Chemistry 141 Week 3 CHM141
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This 2 page Class Notes was uploaded by Sydney on Sunday September 18, 2016. The Class Notes belongs to CHM141 at Saint Martin's University taught by Brandy R Fox in Fall 2016. Since its upload, it has received 2 views. For similar materials see General Chemistry in Chemistry at Saint Martin's University.
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Date Created: 09/18/16
Monday 9/12 Atomic theory of matter, Atomic structure, Scientific method Real scientific method builds on itself. If a hypothesis is accepted and contribute to body of knowledge. LawIf testing yields constant observations Theory If supporting same hypothesis (cannot prove) supports it. History of the atom Democritus (460390 BC) “Atomos” building blocks Plato/ Aristotle Theory without atomos, Atomic view of matter faded for 100’s of years Sir Isaac Newton (16421727) Air is something invisible but in constant motion Brought back atomic theory. Dalton “Grandfather of Chemistry” linked idea of atom to elements. Quantified atomic theory. 1.Each element composed of atoms 2. Each atom is the same in the element, different from all other elements 3. Elements of one atom can not be changed into atoms of a different element 4. Compounds are formed when atoms combine. Compounds always have same composition. ↳ Predicted when A and B for compound will have small whole numbers. No A 3.45Law of multiple proportions Put together first table of related masses of the elements 1858 Chemists solved problem of correct determination of molecular formulas and atomic masses. Atoms If you take apart atom, the subatomic parts to not act like the element J.J ThomsonWith cathode ray found ray bent. There must be a magnetic field When he put negative/positive plates, it bent towards positive meaning the force was negatively charged. Forced ray to go straight to calculate mass to charge ration ray was identical for any cathodeElectrons are universal MillikanOil drop experiment. Measured rate of oil droplets falling on negatively charged plate. Found they were all multiples, knew charge so could calculate mass. Pudding modelNegative particles in large positive field. ↳To test: Shot positive charge though gold foil. Expected to see little change in path. After testing. Some shot back at him. ↳Nucleus proposed Cloud of electrons around large lump of positive particles. Particle Charge Mass P Proton 1.602 x 10 19 1.0073 amu N Neutron 0 1.0087 amu e Electron 1.602 x 10 19 5.486 x 10 4 Atoms have charges of equal and opposite amounts Every atom is neutral overall #p=#e All mass is in the center because P+N reside in nucleus e are attracted to positive charge Diameter of atom Between 1 x 10 to 5 x 10 10 10 4 Angstrom Å=1 0 m o atom is between 15 Å nucleus between 1 0 Atom is mostly empty space. Nucleu is dense, 10 to 10 g/cm13 14 3 Atomic number determined by number of protons Isotopes 2 atoms with same # of protons, different # of neutrons Or 2 atoms of same element with different mass. 12C is carbon 12. Top number is atomic mass, #p+#n. Bottom number is atomic number 6 Atomic mass (or atomic weight) is a weighted average. Abundance x mass of isotope Ion When #p ≠ #e properties very different from that of parent Want to be like noble gas with full valence electrons anionwhen add electrons becomes more negative Cation when subtract electrons becomes more positive Bonding Covalent2 nonmetals sharing e Molecular compound. Ionic Usually metal and nonmetal cation and anion. Exchange of electrons electrostatic attraction between charged species. Metallic 2 metals. “Sea of electrons” solid metal Valence electrons All involve outer electrons Ionic compounds NaClAttracted. Lattice where cation surrounded by anions. All connected. Report formula with smallest ration Molecular compounds Discrete molecules. Could pick up a compound.. Not a lattice Report formula in the number of each type of element Octet rule: Atoms tend to gain/lose/share e until surrounded by 8. (2 for H, Li, B) Na1 valence electron Lewis dot structure Na∙ + Would like to form 1 cation by losing it’s 1 valence electron Knowing that compound must be neutral can deduce charge of unknown. 4+ PtCl4Know Cl is negative, wants to gain an electron so Pt is