ORGANIZING ELEMENTS

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ORGANIZING ELEMENTS

• A little history of how the periodic table was
  created

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Ways to Organize elements

• 1. By State
• Most elements are SOLID
• 11 are gases
• 2 are liquids
• 2. By Colour and Appearance
• Majority of elements are SILVERY, SHINY solids

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• 3. Organization into Metals and Non-metals
• Metals
• Shiny
• Good conductors of electricty
• Malleable
• Ductile
• Non-metals
• Not shiny
• Poor conductors
• Brittle
• Semi-metals (metalloids)
• Elements that possess some properties associated
  with metals
• 4. Organize by Reactivity
• Noble Gases - inert
• 5. Organization by Atomic Mass
• Organize by relative atomic mass

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Periodic Table of the Elements

• Johann Dobereiner 1829 Law of Triads
• Regularity in atomic mass of chemically and
  physically similar elements
• Example Li, Na, K
• All soft, very reactive metals
• Difference in atomic masses -gt 16.1
• BUT regularity did not generally apply

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• John Newlands 1864 - Law of Octaves
• Arranged known elements in order of increasing
  relative atomic mass
• Every 8th element had similar chemical and
  physical properties
• BUT only worked for first 20 elements

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• Dmitri Mendeleev - 1869
• properties of the elements are periodic
  functions of their relative atomic masses
• Able to organize elements into subgroups
• Left blank spaces
• Able to predict elements that had yet to be
  discovered
• BUT some inconsistencies
• Example Te (127.6), I (126.9)
• Physical and chemical properties suggest that the
  order be reversed

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• Henry Moseley - 1912
• elements are arranged in order of increasing
  atomic number
• Periodic repetition of elements with similar
  properties
• Currently accepted periodic table

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Current Organization of the Periodic Table
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Periodic Table Jargon

• Group/Family- the columns in the periodic table.
• Period- the rows of the periodic table

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Metals vs Nonmetals

• No metallic luster, and do not reflect light.
• Very brittle
• Not able to conduct electricity or heat very
  well.
• Cannot be rolled into wires or pounded into
  sheets.

• Shiny, lustre
• Hard
• Good conductors of heat/electricity
• metals are malleable, ductile,

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Metalloids

• Substances that have metal and non metal
  properties.
• Some of the metalloids, such as silicon and
  germanium, are semi-conductors. This means that
  they can carry an electrical charge under special
  conditions.

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ALKALI METALS

• Li, Na, K, Rb, Cs
• High chemical reactivity
• Reacts vigorously with water
• Reactivity of Metal Increases as you go down
  the periodic table
• Hardness of Metal Decreases as you go down the
  periodic table
• Melting Point of Metal Decreases as you go down
  the periodic table

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ALKALINE EARTH METALS

• Be, Mg, Ca, Sr, Ba, Ra
• show similar trends as Alkali Metals

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Halogens

• F, Cl, Br, I
• Reactivity of Non-metallic elements Decreases
  as you go down the periodic table.
• Boiling Point and Melting Point Increase as you
  go down the periodic table.

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NOBLE GAS FAMILY

• He, Ne, Ar, Kr, Xe, Rn
• inert, low reactivity
• do not form stable compounds with other elements
• electron arrangement is stable

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Trends Across A Row of Elements

• each row is called a PERIOD
• In general - reactivity is lowest in the middle
  of a period and increases toward either end
  (disregarding Noble Gases)