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Chapter 2

Molecules. +. Ions. Atoms. Chapter 2. Atoms. History Recap:. Democritus -indivisible atom Dalton -indivisible atom, all atoms of the same element are identical, atoms are rearranged to make new compounds

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Chapter 2

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  1. Molecules + Ions Atoms Chapter 2

  2. Atoms History Recap: • Democritus-indivisible atom • Dalton-indivisible atom, all atoms of the same element are identical, atoms are rearranged to make new compounds • J.J. Thomson-experiments with cathode ray tubes led to his discovery of the first sub-atomic particle, the electron. (plum-pudding model). • Millikan-oil drop experiment determined the charge on the electron (1.602 x 10-19 C) • Rutherford-gold foil experiment established that the atom contains a small, very dense nucleus; goes on to discover protons. • Chadwick-discovers neutrons which explains atomic#/atomic mass discrepancies.

  3. Atomic Structure: Particle Charge (C) Mass (amu) Mass (g) Proton +1.602 x 10-19 1.0073 1.6727 x 10-24 Neutron 0 1.0087 1.6750 x 10-24 Electron -1.602 x 10-19 5.486 x 10-4 9.109 x 10-28 1 amu = 1.66054 x 10-24 g 1 g = 6.02214 x 1023 amu Typical atomic diameter: = 1  5 Å = 100  500 pm = 1 x 10-10 5 x 10-10 m

  4. Atomic number = The number of protons in an atom #protons + #neutrons in an atom Mass number = Isotopes = Atoms of the same element, but different mass# Allotropes = Different structural forms of the same element Ex: graphite, diamond, fullerenes are all C Nuclide = An atom of a specific isotope Ex: 14C vs. 12C Atomic mass = The weighted average of the mass numbers for all of the element’s isotopes Ex: Carbon is composed of 98.93% C-12 and 1.07% C-13. The masses of these isotopes are 12 amu and 13.00335 amu. Atomic mass = (0.9893)(12) + (0.0107)(13.00335) = 12.01 amu

  5. Magnet Detector Accelerating grid 37Cl+ Heated filament Beam of positive ions 35Cl+ Sample Separation of ions based on mass differences Ionizing electron beam Mass spectrometer: Measures atomic and molecular weights The ratio of the height of the peaks is the same as the %abundance for the different nuclides.

  6. Metalloid Metals Nonmetals 1 8 # Valence electrons 2 3 4 5 6 7

  7. Alkali metals Noble gases Chalcogens Halogens Pnictogens Alkaline earth metals Transition Metals (Rare Earths) Inner Transition Metals Lanthanides Actinides

  8. Molecules + = two or more atoms covalently bonded together to form a discrete particle Nomenclature 6 H2O Water (aka dihydrogen monoxide) 6 CO2 Carbon dioxide C6H12O6 glucose

  9. Simple Organic Nomenclature: organic compounds are named after the number of carbon atoms they contain AND for any functional groups that might be present #C atoms Root name Root name #C atoms 1 Meth- 6 Hex- 2 Eth- 7 Hept- 3 Prop- 8 Oct- 4 But- 9 Non- 5 Pent- 10 Dec-

  10. Alkenes: Like an alkane except it contains at least one C=C double bond. Name is Root + ene Functional Groups Alkanes: Molecule contains only C and H bonded with single bonds. Name is Root + ane methane ethane propane propadiene ethene propene

  11. Alcohols: Alkane and an –OH group. Name Root + an + ol Methanol (wood alcohol) Ethanol (Grain alcohol) Propanol Structural isomer: two or more different ways to place the functional group on the carbon backbone. 2-propanol or isopropanol (rubbing alcohol)

  12. Ketones: Like alcohols except that the oxygen is bonded to a nonterminal carbon with a double bond. Name is Root + an + one 2-propanone (acetone) 2-butanone 3-pentanone 3-methyl-2-butanone 2-pentanone

  13. Carboxylic acids: alkane + a COOH ( ) group. Name is Root + anoic acid Methanoic acid (formic acid) Ethanoic acid (acetic acid) Propanoic acid Butanoic acid (rancid butter) 2-methyl-propanoic acid

  14. mass of C mass of H mass of cmpd mass of cmpd %C = 2(12.011) x 100 = 85.62% %C = %H = x 100 x 100 2(12.011)+4(1.0079) What are the molecular formulas for the molecules shown below? C3H6 C4H8 C2H4 If we were to analyze compound #1, what %mass C and H would we get for it ? %H = 14.37%

  15. mass of C mass of H mass of cmpd mass of cmpd %C = %H = x 100 x 100 What is the %C and %H for the second two compounds? C3H6 C4H8 C2H4 %C = 85.62% %H = 14.37% %C = 85.62% %H = 14.37% %C = 85.62% %H = 14.37% The simplest whole number ratios of COVALENT compounds gives you the empirical formula for the compound.

  16. What is the empirical formula for a compound that is: 47.0% K 14.5% C 38.5% O 47.0 g K 1 mole K = 1.2 moles K 1 mole K 39.0983 g 1 mole C 14.5 g C 1 mole C = 1.2 moles C 12.011 g 1 mole O 38.5 g O = 2.4 moles O 2 moles O 15.9994 g Divide through by smallest molar amount (1.2 moles) The empirical formula is: KCO2

  17. Determine the molecular formula: 1) 5.9 mol H : 5.9 mol O molar mass: 34.02 g/mol Empirical formula: HO Molar mass = 17.01 g/mol Molecular formula: H2O2 2) 1.2 mol K: 1.2 mol C: 2.4 mol O molar mass: 166.22 g/mol Empirical formula: KCO2 Molar mass = 83.11 g/mol (Divide molecular gfm by empirical gfm = 2) Molecular formula: K2C2O4

  18. Oxidation Numbers of Representative Elements +1 +2 +3 -3 -2 -1

  19. When NONMETALS and METALS combine together, they TRANSFER electrons to form IONIC bonds. Ions -1 +1 Cl Na + Sodium has LOST one of its electrons in the transfer…it is now a monovalent cation (has a +1 charge). Chlorine has GAINED one extra electron in the transfer…it is now a monovalent anion (has a -1 charge). Q: What is the formula for… Calcium chloride? CaCl2 Ba3P2 Magnesium oxide? MgO Barium phosphide?

  20. Warming up with a few ionic compounds: 1. Ca2C Calcium carbide 2. (NH4)3PO4 Ammonium phosphate 3. Mg(OH)2 Magnesium hydroxide Potassium oxide 4. K2O 5. NH4Cl Ammonium chloride Tin(II) nitrate 6. Sn(NO3)2 Iron(II) hydrogen phosphate 7. FeHPO4 Copper(I) sulfide 8. Cu2S Nickel(II) acetate 9. Ni(C2H3O2)2 Mercury(I) perchlorate 10. HgClO4

  21. Cooling down with some acid naming: 1. HNO3 Nitric acid 2. HBr Hydrobromic acid 3. H2SO4 (battery acid) Sulfuric acid 4. HF (dissolves glass) Hydrofluoric acid 5. HClO4 Perchloric acid (ignites organic cmpds) 6. H2SO3 Sulfurous acid 7. HBrO3 Bromic acid 8. HCl (stomach acid) Hydrochloric acid 9. H3PO4 Phosphoric acid (acid in colas) 10. HClO Hypochlorous acid

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