The Periodic Table

1
The Periodic Table
2
Discovering a Pattern

• Dmitri Mendeleev- Russian Chemist- discovered a
  pattern to the element in 1869
• First he arranged them by different properties
  (density, appearance, MP).
• After much thought he arranged them in order of
  increasing atomic mass.
• When he did that a pattern appeared!!!!

3
Periodic Properties of the Elements

• When arranged in order of increasing atomic mass,
  those that had similar properties occurred in a
  repeating pattern.
• Periodic-happening at regular intervals
• Mendeleev found that the elements properties
  followed a pattern that repeated every 7 elements.

4
Predicting Properties of Missing Elements

• Mendeleev predicted that elements yet to be found
  would fill in the gaps of the pattern
• He used the pattern to predict their properties
• By 1886 all the gaps had been filled and his
  predictions were correct!

5
Changing the Arrangement

• A few elements did not fit the pattern in
  Mendeleevs table
• Mendeleev thought if he found a more accurate
  atomic mass than he would fix the flaws in his
  table. But his masses were correct.
• Henry Moseley-determined the of protons-the
  atomic -
• All elements fit the pattern in the table when
  arranged buy atomic .
• Periodic Law- repeating chem. phys. Properties
  of elements change periodically with the elements
  atomic

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Metals

• Most Elements
• Found LEFT of the zigzag line on the table
• Few electrons in their outer energy level
• Most are solid at room temp. Mercury is an
  exception-It is liquid at room temp.
• Shiny
• Ductile-drawn into thin wires
• Good conductors of electric current
• Good conductors of thermal energy
• Malleable- flattened with a hammer and wont
  shatter

7
Nonmetals

• Found right of the zigzag line on the table
• Almost a complete set of electrons in their outer
  level.
• Atoms of the elements in Group 18 (noble
  gases)-have a complete set of electrons
• More than ½ are gases at room temp.
• Many properties of nonmetals are opposite of
  metal properties
• Not malleable or ductile, not shiny, poor
  conductors of thermal energy and electric current

8
Metalloids

• Can also be called semiconductors.
• These border the zigzag line on the table.
• About ½ have a complete set of electrons in their
  outer energy level
• Have properties of both metals and nonmetals
• Ex Tellurium is shiny BUT it is brittle
• Ex Boron-very hard but also very brittle, at
  high temps. It is a good conductor of electric
  current

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Chemical Symbols

• Each element is identified by a chemical symbol.
  Symbols are worldwide.
• Some elements are named after scientists, some
  are named after places. Some names may vary by
  country.
• One or two letters. The first letter is always
  capitalized.
• Newest elements have temporary three letter
  symbols

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Rows And Columns

• Horizontal rows (from left to right) are called
  PERIODS
• Physical and Chemical Properties in a row follow
  a periodic pattern as you move across.
• Conductivity and reactivity change gradually as
  you move left to right

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Rows And Columns

• Vertical columns (top to bottom) are called
  GROUPS
• Elements in the same group often have similar
  chemical and physical properties.
• A group is also called a FAMILY