Further discoveries in the development of Atomic Theory

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• Further discoveries in the development of Atomic
  Theory
• Conservation of mass (conservation of mass
  energy)
• Law of definite proportions the composition of
  the same pure substance always contains the same
  elements in the same proportion by mass
• Example
• CH4 natural gas (odorless, tasteless,
  colorless)
• CH4 O2 CO2 H2O heat

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• Further discoveries in the development of Atomic
  Theory
• Conservation of mass (sort of)
• Law of definite proportions the composition of
  the same pure substance always contains the same
  elements in the same proportion by mass.
• Law of multiple proportions the same two
  elements can combine to form different compounds.
  However the ratio of the mass of one element that
  combines with a fixed amount of the second
  element is always in the ratio of whole numbers.
  

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ethane 1gH/4gC ethylene 0.71g H/4.29gB How
much combines with 1 g of H? 0.71g H/4.29g C
1g H/x C x C 6.0g benzene 0.39g H/4.61g C
How much combines with 1 g of H? 0.39g H/4.61g
C 1g H/xg C xg C 12 g The amount of carbon
that combines with 1 g of hydrogen is in the
ratio of whole numbers 236 (or equivalently,
4 6 12)

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• Naming Chemical Compounds
• The metal is named first followed by the name of
  the non metal An alternative way of looking at
  this is the cation () is named before the anion
  (-)
• Binary Compounds
• NaCl
• sodium chloride (sodium and chlorine)
• LiF
• lithium fluoride (lithium and fluorine)
• KBr
• potassium bromide (potassium and bromine)
• CaO
• calcium oxide (calcium and oxygen)
• 5. ZnS
• zinc sulfide (zinc sulfide)

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• More Complex Compounds
• Na2O
• sodium oxide
• 2. Ba(OH)2
• barium hydroxide
• 3. H2S
• hydrogen sulfide
• 4. CO
• carbon monoxide
• CO2
• carbon dioxide
• 6. SO3
• sulfur trioxide

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• Chemical Bonding
• Why are most elements in the periodic table found
  combined?
• Combined elements must be more stable under
  enviromental conditions
• What is the nature of the bonding found between
  different elements in
• CO, CH4, CO2?
• covalent
• 2. NaCl-, CH3CO2-1K, Zn2CrO4-2
• ionic and ionic and covalent
• 3. Na, Fe, Mg, Zn
• metallic (a special case of covalent bonding and
  ionic bonding)

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• What do we mean by these terms ionic, metallic
  and covalent?
• Covalent bonding bonding between two or more
  elements by mutual sharing of electrons, but not
  necessarily equally.
• Ionic bonding bonding that occurs as a result of
  transfer of an electron from one element to
  another. This type of bonding is generally
  observed only in the solid state and in very
  polar liquids such as water. In the gas phase,
  bonding is generally more the result of electron
  sharing.
• Bonding in metals Bonding in metals is more
  difficult to describe but does involve sharing of
  electrons. In metals it is more difficult to
  associate specific electrons as belonging to a
  particular element.

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1. Why do different elements need to form
different types of bonds? Not all elements
readily form bonds. The inert gases are found in
nature uncombined. Since these elements have
differing number of protons and more importantly,
different number of electrons surrounding the
nucleus, a study of how the electrons are
distributed in space may give us a clue as to why
these elements (the inert gases) are un-reactive
and also why other element are reactive. However
we will defer this discussion until later
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One way of looking at covalent bonding
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Some examples of molecules with covalent bonding
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NaCl an example of a substance with ionic bonding
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Despite the fact that metals form stable bonds
with each other, this doesnt mean that they
cannot be unreactive toward other
substances. Take for example Al and I2 CCA3
D\MOVIES\METALI1 Chapter 1 visuals
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Common bonding exhibited by various elements in
the periodic table column number in periodic
table common charge ( ) if ionic Alkali
metals 1 (1) 1 bond with other
nonmetals Alkaline earths 2 (2) 2 bonds
with other nonmetals Metaloids 3 (3) 3
bonds with other nonmetals or
metals Nonmetals Group 4 4 bonds Non-metals
Group 5 (-3) 3 bonds with nonmetals or
metals Non-metals Group 6 (-2) 2 bonds
usually with metals Non-metals Group 7 (-1) 1
bond with metal or nonmetal Inert Gases Group
8 0 bonds with anything Transition metals
(2, other) 2 bonds with nonmetals
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Water H2O Water is probably the most unique and
anomalous chemical substance in the universe.
Without it life would not be possible. Our bodies
are approximately 70 H2O. The properties of
water are anomalous in comparison to similar
compounds formed by other elements. H2O H2S, N
H3, PH3, CH4, HF Melting point (K) 273 191 196 1
85 90 190 Boiling temperature (K)
373 213 240 281 112 293 Solvent
properties
In the presence of water, may substances undergo
substantial changes
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The Effects of H2O on Some Substances HCl
(gas) covalent bonding H2SO4 (concentrated,
liquid) covalent bonding H3PO4 (liquid)
covalent bonding When H2O is added to any of
these three compounds, the following happens HCl
H2O H3O Cl- 2H2SO4 3H2O
2H3O HSO4- SO4-2 H3PO4 H2O H3O
H2PO4-
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Acids and Bases Acid A substance that readily
gives up a hydrogen ion (H). Generally we refer
to an acid as something that gives up a proton to
water to form a hydronium ion, simply written as
H3O. Base A substance that readily picks up or
abstracts a hydrogen ion (H). Generally we
refer to a base as a substance that picks up a
proton to water to form a neutral substance,
often H2O. Acid Base Salt
Water
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strong
strong
strong
strong