Elements and The Periodic Table

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Elements and The Periodic Table
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Classification of Matter
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History of the Periodic Table

• 330 B.C - 4 elements
• 1800 - 31 elements
• 1865 - 63 elements
• Chemists required a systematic method to organize
  the elements

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Johann Dobereiner

• 1829
• Law of Triads
• Groups of 3 elements with similar properties

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John Alexander Newlands

• 1864
• Arranged all known elements in order of
  increasing atomic mass
• Observed that every 8th element had similar
  physical and chemical properties (Law of Octaves)
• Began to group these elements into families

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Julius Lothar Meyer

• 1865
• Also arranged the elements in order of increasing
  atomic mass
• Found repeating patterns and developed a table of
  elements

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Dimitri Mendeleev

• 1869
• Credited as the Father of the Periodic Table
• Periodic Law When arranged by atomic number, the
  properties of the elements repeat at regular
  intervals.

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and the same number of valence electrons
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Hydrogen(A class of its own)

• Sometimes it behaves like an alkali metal,
  sometimes like a halogen, and sometimes in its
  own unique way.

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Group 1 Alkali Metals

• 1 valence electron (electrons in their outermost
  shell)
• Soft, shiny, easily cut with a knife
• The most reactive metals
• React violently with water (stored in oil or a
  vacuum)
• React with halogens to form salts

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Group 2 Alkaline Earth Metals

• 2 valence electrons
• Light, reactive metals

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Groups 3-12 Transition Metals

• 1 or 2 valence electrons
• Strong, hard metals
• Good conductors of heat and electricity
• Wide range of chemical and physical properties

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Group 17 Halogens

• 7 valence electrons
• Extremely reactive nonmetals

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Group 18 Noble Gases

• Full outer shell
• Extremely unreactive (inert)

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Lanthanides (Rare Earth Metals)

• Elements 57-70

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Actinides

• Elements 89-102
• Transuranic Elements Synthetic elements
• (elements 93)