Honors chemistry
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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

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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 table

    2.4 Periodic Table


    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)

      • CuprousCupric


    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  -icHClO3 = chloric acid

      • -ite  -ousHClO2 = 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 H2Obarium chloride dihydrate

    • Try this: CuSO4∙ 5 H2O


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