The History of the Modern Periodic Table

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The History of the Modern Periodic Table
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chlorine
nitrogen
silver
gold
mercury
oxygen
hydrogen
helium
sodium
niobium
neodymium
carbon
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Elements

• Science has come along way since Aristotles
  theory of Air, Water, Fire, and Earth.
• Scientists have identified 90 naturally occurring
  elements, and created about 28 others.

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During the nineteenth century, chemists began to
categorize the elements according to similarities
in their physical and chemical properties. The
end result of these studies was our modern
periodic table.
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???? 1829, Johann Dobereiner
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(ex. Cl, Br, I and Ca, Sr, Ba)
Model of triads
1780 - 1849
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1800s - Dobereiner
Two of Dobereiners Triads Two of Dobereiners Triads Two of Dobereiners Triads
Element Atomic Mass Unit (amu) Density (g/mL)
Cl 35.5 1.56
Br 79.9 3.12
I 126.9 4.95

Ca 40.1 1.55
Sr 87.6 2.6
Ba 137 3.5

• The figure shows the atomic masses and densities
  of the elements in two of Dobereiners triads.

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In 1863, John Newlands
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Law of Octaves
1838 - 1898
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1800s - Newlands
Newlands Law of Octaves Newlands Law of Octaves Newlands Law of Octaves Newlands Law of Octaves Newlands Law of Octaves Newlands Law of Octaves Newlands Law of Octaves
1 2 3 4 5 6 7
Li Be B C N O F
Na Mg Al Si P S Cl
K
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Dmitri Mendeleev and Lothar Meyer
In 1869 he published a table of the elements
organized by increasing atomic mass.
1830 - 1895
1834 - 1907
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1800s - Mendeleev
Ekasilicon and Germanium Ekasilicon and Germanium Ekasilicon and Germanium
Property Ekasilicon Germanium
atomic mass (amu) 72 72.59
density (g/cm3) 5.5 5.35
melting point (oC) high 947
color gray gray
The properties that that Mendeleev predicted for
ekasilicon closely match the actual properties of
germanium.
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Henry Moseley
In 1913, through his work with X-rays, he
determined the actual nuclear charge (atomic
number) of the elements. He rearranged the
elements in order of increasing atomic number.
There is in the atom a fundamental quantity
which increases by regular steps as we pass from
each element to the next. This quantity can only
be the charge on the central positive nucleus.
1887 - 1915
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The Periodic Law

• How is the modern periodic table organized?
• In the modern periodic table, elements are
  arranged in order of increasing atomic number.
  (problems with Medeleevs method)

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Metals, Nonmetals, and Metalloids

• Metals, Metalloids, and Nonmetals in the Periodic
  Table

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Metals, Nonmetals, and Metalloids

• Metals are good conductors of heat and electric
  current.
• 80 of elements are metals.
• Metals have a high luster, are ductile, and are
  malleable.

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Metals, Nonmetals, and Metalloids

• Nonmetals
• In general, nonmetals are poor conductors of heat
  and electric current.
• Most nonmetals are gases at room temperature.
• A few nonmetals are solids, such as sulfur and
  phosphorus.
• One nonmetal, bromine, is a dark-red liquid.

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Metals, Nonmetals, and Metalloids

• Metalloids
• A metalloid generally has properties that are
  similar to those of metals and nonmetals.
• The behavior of a metalloid can be controlled by
  changing conditions.

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Electron Configurations in Groups

• Electron Configurations in Groups
• ????????????????????????????????????? electron
  configurations
• Elements can be sorted into noble gases,
  representative elements, transition metals, or
  inner transition metals based on their electron
  configurations.

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Electron Configurations in Groups

• The Noble Gases
• The noble gases are the elements in Group 8A of
  the periodic table. The electron configurations
  for the first four noble gases in Group 8A are
  listed below.

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Electron Configurations in Groups

• The Representative Elements
• Elements in groups 1A through 7A are often
  referred to as representative elements because
  they display a wide range of physical and
  chemical properties.
• The s and p sublevels of the highest occupied
  energy level are not filled.
• The group number equals the number of electrons
  in the highest occupied energy level.

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Electron Configurations in Groups

• In atoms of the Group 1A elements below, there is
  only one electron in the highest occupied energy
  level.
• In atoms of the Group 4A elements below, there
  are four electrons in the highest occupied energy
  level.

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Transition Elements

• Blocks of Elements

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Representative Elements
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Representative Elements
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• Martin S. Silberberg, Chemistry The Molecular
  Nature of Matter and Change, McGraw-Hill Higher
  Education, 2004
• Raymond Chang, Chemistry, Williams College,
  McGraw-Hill Higher Education, 2002