Ancient Philosophy

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Ancient Philosophy

• Matter to be composed of four basic elements
• Earth, water, wind, and fire
• Two schools of thought regarding matter
• Aristotle, Pluto, and their followers regarded
  matter to be continuous and infinite
• Democritus, Leucippus, and their followers
  considered matter to be made up of some basic
  units they called atomos (or atoms)

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Combustion and the Phlogiston Theory

• A log is burned
• the mass of the ash formed is much less than the
  log
• What happen to the rest of the mass?
• Early 18th century chemists considered that
• materials burn because they contains a kind of
  substance that they called phlogiston
• combustion is a process that caused the loss of
  phlogiston
• thus, the mass of ash is less than the log.

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Experimental Science versus Philosophy

• Antoine Lavoisier (1743-1794) performed
  quantitative experiments that
• debunked the phlogiston theory
• Showed combustion is a chemical process that
  involves reaction with oxygen
• Showed mass is neither created nor destroyed
  during chemical reactions.
• Joseph Proust (1754-1826) also performed
  quantitative experiments and showed that the
  composition of a given compound is constant.
• The composition of pure copper carbonate is
  always 51 Cu, 10 C, and 39 O

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Fundamental of Chemical Laws

• Lavoisiers quantitative experiments provide the
  basis for the law of conservation of mass
• In chemical reactions, mass is neither created or
  destroyed
• Prousts work became the law of definite
  proportion (or law fixed composition)
• A given compound always contains the same types
  of elements in a fixed composition by mass,
  regardless of its origin.

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Daltons Atomic Theory

• Elements are made up of atoms
• Atoms of the same element are identical
• Atoms of different elements are different
• Compounds are formed when atoms of different
  elements combined in simple whole number ratios
• A given compound always contains the same number
  and type of its atoms
• Atoms are not created or destroyed in chemical
  reactions.

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Principle of Chemical Combination

• Law of Multiple Proportion
• When two elements react to form more than one
  type of compounds, there exist a simple ratio of
  the masses of one of the elements that combine
  with a fixed mass of the other element in these
  compounds
• Example Carbon reacts with oxygen to form two
  compounds. In one, 1.00 g of carbon combines with
  1.33 g of oxygen, and in the other, 1.00 g of
  carbon combines with 2.66 g of oxygen. The mass
  ratio of oxygen in the two compounds is 12.

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Principle of Chemical Combination

• Gay-Lussacs Law of Combining Volumes
• In reactions involving gaseous reactants and
  products, there exist simple ratios of their
  volumes measured under the same temperature and
  pressure.
• Examples
• 1 volume of hydrogen reacts with 1 volume of
  chlorine to form 2 volumes of hydrogen chloride
• 2 volumes of hydrogen reacts with 1 volume of
  oxygen to form 2 volumes of water vapor.

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Interpretation of Gay-Lussacs Experiments

• Note under same temperature and pressure, equal
  volumes of gases contain the same number of
  molecules
• 1 L of hydrogen 1 L of chlorine ? 2 L of
  hydrogen chloride implies
• 1 H-molecule 1 Cl-molecule ? 2 HCl molecules.
• Then, each of hydrogen and chlorine molecule
  should consists of 2 atoms, and the reaction may
  be written using the following equation
• H2(g) Cl2(g) ? 2 HCl(g)

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Interpretation of Gay-Lussacs Experiments

• (Under same temperature and pressure, equal
  volumes of gases contain the same number of
  molecules.)
• 2 L of hydrogen 1 L of oxygen ? 2 L of water
  vapor implies
• 2 H-molecules 1 O-molecule ? 2 water molecules.
• then, each hydrogen and oxygen molecule should
  consists of 2 atoms (H2 and O2), while formula of
  water would be H2O.
• The reaction forming water can be represented by
  the equation
• 2H2(g) O2(g) ? 2 H2O(g)

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Atomic Structure

• Characteristics of cathode-ray
• It originates from the cathode plate
• The beam bends when it passes through an electric
  or magnetic field, which implies negatively
  charged particles
• The charge-to-mass ratio is constant, at -1.76 x
  108 C/g, regardless of the materials used
• Cathode ray is actually a beam of electron.

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Atomic Model-1

• Plum-pudding model
• Atom is composed of diffused mass (like a cotton
  ball) of positive charge, with electrons loosely
  embedded on its surface
• The number of electrons present is equal to the
  magnitude of unit positive charges in the atom.

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Atomic Model-2

• The Nuclear Model
• Atom contains nucleus, which is composed of
  positively charged protons and neutral neutrons
• The mass of the atom is concentrated in the
  nucleus
• The nucleus is much, much smaller than the atom
• Electrons occupy the vast empty space
  surrounding the nucleus
• Proton or neutron is about 1840 times larger
  (more massive) than electron

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Relative and Absolute Masses

• Proton 1.007276 amu 1.673 x 10-27 kg.
• Neutron 1.008665 amu 1.675 x 10-27 kg.
• Electron 0.000549 amu 9.109 x 10-31 kg.

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Relative and Absolute Charges

• Proton 1 1.602 x 10-19 C
• Neutron 0
• Electron -1 -1.602 x 10-19 C

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Isotopes

• Atoms from same element that have different
  masses
• Atoms containing the same number of protons but
  different number of neutrons
• Atoms that have the same atomic number (Z) but
  different mass number (A)
• Atomic number (Z) number of protons
• Mass number (A) of protons of neutrons
• Number of neutrons (A Z)

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Molecules and Ions

• Molecule
• A neutral species containing two or more atoms
  bound together (chemically).
• Ions
• electrically charged particles, either positive
  (called cation) or negative (called anion)
• atoms may lose electrons to form cations, or may
  gain electrons to form anions.

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Periodic Table

• Table is divided into 18 columns called groups
  and 7 rows called periods.
• Groups are numbered 1 18 in the IUPAC
  nomenclature, or 1A 8A and 1B 8B in the ACS
  nomenclature.
• Along each period (left to right), elements are
  arranged in increasing atomic number
• Within each group, elements share similar
  chemical characteristics.

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Major Classifications of Elements

• Metals
• Mainly solid, except for mercury have shiny
  appearance
• Good conductors of heat and electricity
• Malleable and ductile
• Nonmetals
• Mainly gases, one (bromine) is a liquid, and a
  few solids
• Generally poor conductors of electricity
• Solids are generally brittle and not lustrous.

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Other Classifications of Elements

• Metalloids (semi-metals)
• Very hard (covalent network) solids
• physically look like metals, but chemically
  behave like nonmetals
• Main group elements
• Elements of Group 1 (1A alkali metals), 2 (2A
  alkaline Earth metals), 13 (3A), 14 (4A), 15
  (5A), 16 (6A), 17 (7A the halogens), and 18 (8A
  noble gases)
• Transition metals
• Elements of Group 3 (3B) 12 (2B) contains
  heavy metals.

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Other Classifications of Elements

• Lanthanide series
• Elements after lanthanum (La) Ce, Pr, Nd, Pm,
  Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu
• Actinide series
• Elements after actinium (Ac) Th, Pa, U, Pu, Am,
  Cm, Bk, Cf, Es, Fm, Md, No, and Lr
• Mostly synthesized in particle accelerators and
  all are radioactive

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Nomenclature

• Type-I (ionic) compounds
• contain Group 1 metals, Group 2 metals, aluminum,
  or galium, combining with nonmetals
• Type-II (ionic) compounds
• contain transition metals, In, Sn, Tl, Pb, or any
  of the lanthanide or actinide series metals,
  combining with nonmetals
• Type-III (molecular) compounds
• contain only nonmetals or metalloids and
  nonmetals

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Type-I (Ionic) Compounds

• Binary compounds
• NaCl sodium chloride
• MgF2 magnesium fluoride
• Al2O3 aluminum oxide
• Compounds containing polyatomic ions
• CaSO4 calcium sulfate
• NaHCO3 sodium hydrogen carbonate
• KNO3 potassium nitrate

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Type-II (Ionic) Compounds

• Binary compounds
• FeCl2 iron(II) chloride FeCl3 iron(III)
  chloride
• CrO chromium(II) oxide Cr2O3 chromium(III)
  oxide
• Compounds containing polyatomic ions
• Co(NO3)2 cobalt(II) nitrate
• Co(NO3)3 cobalt(III) nitrate
• Pb(C2H3O2)2 lead(II) acetate
• Pb(C2H3O2)4 lead(IV) acetate

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Type-II Compounds Naming System

• Formula Stock System Old System
• CrO - chromium(II) oxide chromous oxide
• Cr2O3 - chromium(III) oxide chromic oxide
• Fe(NO3)2 Iron(II) nitrate Ferrous nitrate
• Fe(NO3)3 Iron(III) nitrate Ferric nitrate

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Naming Acids

• Binary Acids (without oxygen in the formula)
• Hydro first syllable of anion ic acid
• HF hydrofluoric acid (weak)
• HCl hydrochloric acid (strong)
• HBr hydrobromic acid (strong)
• HI hydroiodic acid (very strong)
• H2S hydrosulfuric acid (weak)
• HCN hydrocyanic acid (very weak)

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Naming Acids

• Oxoacids
• HNO3 nitric acid (strong)
• HNO2 nitrous acid (weak)
• H2SO4 sulfuric acid (strong)
• H2SO3 sulfurous acid (weak)
• H3PO4 phosphoric acid (weak)
• H3PO3 phosphorous acid (very weak)

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More on Oxoacids

• HClO hypochlorous acid (very weak)
• HClO2 chlorous acid (weak)
• HClO3 chloric acid (moderate)
• HClO4 perchloric acid (very strong)
• HBrO4 perbromic acid (strong)
• HIO4 periodic acid (strong)