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Honors Chemistry. Chapter 2: Atoms and Molecules. 2.1 Atomic Theory. Ancient Greeks Democritus – matter is discontinuous (atomos) Aristotle – matter is continuous (hyle) Joseph Proust (1799)

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honors chemistry

Honors Chemistry

Chapter 2: Atoms and Molecules

2 1 atomic theory
2.1 Atomic Theory
  • Ancient Greeks
      • Democritus – matter is discontinuous (atomos)
      • Aristotle – matter is continuous (hyle)
  • Joseph Proust (1799)
      • Law of Definite Proportions – samples of a compound are always composed of the same proportion by mass
  • Antoine Lavoisier
      • Law of Conservation of Mass
2 1 atomic theory1
2.1 Atomic Theory
  • John Dalton (1803)
      • Elements are made of indivisible particles (atoms) which are identical
      • Compounds are composed of atoms of more than one element combined in whole-number ratios
      • Chemical reaction involves rearranging atoms, not creating or destroying them
  • Law of Multiple Proportions
      • Elements can form different compounds by combining in many whole-number ratios
2 2 structure of the atom
2.2 Structure of the Atom
  • J. J. Thomson (1897)
      • Cathode Ray Tube Experiments
      • Discovered electron
      • e/m = -1.76 x 1011 C/kg
      • Plum Pudding Model
  • Robert Millikan (1908)
      • Resolved e/m ratio
      • Oil Drop Experiment
      • ee = -1.6022 x 10-19 C
      • me = 9.11 x 10-31 kg
2 2 structure of the atom1
2.2 Structure of the Atom
  • Radioactivity
      • Wilhelm Roentgen – discovered x-rays
      • Antoine Becquerel – discovered radioactivity
      • a, b, and g radiation
  • The Proton
      • Discovered in modified CRT (canal rays)
      • ep = +1.6022 x 10-19 C
      • mp = 1.67262 x 10-27 kg
  • The Neutron
      • Discovered by James Chadwick
      • mn = 1.6794 x 10-27 kg
2 2 structure of the atom2
2.2 Structure of the Atom
  • Ernst Rutherford (1910)
      • Attempt to find better model of the atom
      • Gold Foil Experiment
      • Performed by Geiger and Marsden
      • Discovered a nucleus in the atom
  • The Planetary Model
      • Nucleus composed of p+ and n
      • e- orbit nucleus
      • Held by electrostatic force
2 3 particles and isotopes
2.3 Particles and Isotopes
  • Atomic Number (Z)
      • Number of protons
  • Mass Number (A)
      • Number of protons + neutrons
2 3 particles and isotopes1
2.3 Particles and Isotopes
  • Nuclear Symbols
      • 7← mass number Li3← atomic number
      • Protons = 3
      • Electrons = 3 (same as p+ in neutral atom)
      • Neutrons = 7 – 3 = 4
      • Listing Z is redundant and often not done
  • Isotopes
      • Same element, different mass number
      • Example: 35Cl and 37Cl
2 4 periodic table1
2.4 Periodic Table
  • Navigating the Table
      • Period – row across the table
      • Group (or Family) – column down the table
      • Metals, nonmetals, and metalloids
  • Family Names
      • IA – Alkalai Metals
      • IIA – Alkaline Earth Metals
      • “B groups” – Transition Metals
      • VIA – Chalkogens
      • VIIA – Halogens
      • VIIIA – Noble Gases
      • Lanthanides and Actinides
2 5 molecules and ions
2.5 Molecules and Ions
  • Molecules
      • Neutral atoms bonded together
      • Diatomic molecule – contains 2 atoms
      • H2, N2, O2, F2, Cl2, Br2, I2
  • Ions
      • Atom or group of atoms with a charge
      • Cation – positive charge
      • Anion – negative charge
      • Monatomic ion – single atom
      • Polyatomic ion – group of atoms
2 5 molecules and ions1
2.5 Molecules and Ions
  • Monatomic Cations (metals)
      • Group IA: 1+
      • Group IIA: 2+
      • Group IIIA: 3+ (B and Al only)
      • Transition and Post-transition metals:
      • Ag: + Zn, Cd: 2+
      • Most others can form multiple charges
      • Cu+ = copper (I) Cu2+ = copper (II)
      • Cuprous Cupric
2 5 molecules and ions2
2.5 Molecules and Ions
  • Monatomic Anions (nonmetals)
      • Group VIIIA: no charge (noble gases)
      • Group VIIA: 1-
      • Group VIA: 2-
      • Group VA: 3-
      • Group IVA: 4-
      • H: 1-
      • No Roman numerals!
      • Change ending to -ide
2 5 molecules and ions3
2.5 Molecules and Ions
  • Polyatomic ions
      • Oxoanions (element with oxygen):
      • First one discovered: change ending to –ate
      • -ite, per-, and hypo- used for other oxoanions
      • ClO4- perchlorateClO3- chlorateClO2- chloriteClO- hypochlorite
      • not all exist for every element
      • e.g., for N, nitrate and nitrite exist, but no others
2 5 molecules and ions4
2.5 Molecules and Ions
  • 1+
      • NH4+ ammonium
      • Hg22+ mercury (I)
  • 1-
      • OH- hydroxide
      • CN- cyanide
      • MnO4- permanganate
      • SCN- thiocyanate
      • HCOO- formate
      • CH3COO- acetate
      • NO3-, FO3-, ClO3-, BrO3-, IO3-
2 5 molecules and ions5
2.5 Molecules and Ions
  • 2-
      • O22- peroxide
      • C2O42- oxalate
      • S2O32- thiosulfate
      • Cr2O72- dichromate
      • CO32-, SiO32-, CrO42-, SO42-
  • 3-
      • PO43-, AsO43-
2 6 chemical formulas
2.6 Chemical Formulas
  • Molecular Formula
      • Molecular Formula – true formula for a molecule
      • Exact number of atoms in the molecule
      • E. g., O2, O3, NH3
      • Structural formula – shows how atoms are attached to each other
      • H |H – N – H
      • Empirical Formula – shows simplest ratio of atoms
      • C6H12O6 CH2O
2 6 chemical formulas1
2.6 Chemical Formulas
  • Ionic Compounds
      • Two or more ions stuck together
      • Charges must neutralize
      • Sodium chloride = Na+ and Cl-
      • Equal charges, so NaCl
      • Magnesium chloride = Mg2+ and Cl-
      • Need 2 Cl-’s to cancel out each Mg2+
      • MgCl2
      • Simplify when needed, e. g., lead (IV) oxide
      • Try these: aluminum sulfide, iron (III) nitrate
2 7 naming compounds
2.7 Naming Compounds
  • Ionic Nomenclature
      • Name the ions involved!
      • K2SO4 = potassium sulfate
      • Try these: K2O, Ba(ClO3)2, CaCO3, FePO4
  • Molecular Nomenclature
      • -ide ending
      • Greek prefixes for numbers:
      • Mono-, di-, tri-, tetra- penta-, hexa-, hepta-, octa-, nona-, deca-
      • Try these: CO2, CCl4, H2O, SO3, UF6
2 7 naming compounds1
2.7 Naming Compounds
  • Acids
      • Produce H+ ions in water solution
      • Binary acids = hydro – ic acid
      • HCl = hydrochloric acid
      • Oxoacids = change ending of anion
      • -ate  -ic HClO3 = chloric acid
      • -ite  -ous HClO2 = chlorous acid
      • Some polyatomic anions are treated as binary
  • Try these:
      • HBr, HNO3, H2SO3, HClO4, CH3COOH
2 7 naming compounds2
2.7 Naming Compounds
  • Bases
      • Produce OH- ions in water solution
      • Named as any other ionic compound
      • NaOH = sodium hydroxide
      • Ammonia (NH3) also produces OH- ions in water
  • Hydrates
      • Compounds with water molecules attached
      • BaCl2∙ 2 H2O barium chloride dihydrate
      • Try this: CuSO4∙ 5 H2O
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