The Periodic Table

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The Periodic Table

• History
• Key Groups and Families
• Periodic Trends

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Early History of the Development of the Periodic
Table

• Dobereiner Law of Triads (early 1800s)
• Observed the similar properties of calcium,
  barium, and strontium and noticed the atomic mass
  of strontium is about halfway between those of
  calcium and barium
• Grouped these elements into what he called a
  triad
• Later noticed other groups of three elements with
  similar properties

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Early History of the Development of the Periodic
Table

• Newlands Law of Octaves (mid 1800s)
• Arranged elements in order of increasing atomic
  mass
• Noted a repetition of properties every eighth
  element (Law of Octaves)

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Dimitri Mendeleev 1869

• Russian chemist
• Suggested the properties of the elements are a
  function of their atomic masses
• Believed similar properties occurred after
  periods (horizontal rows) that could vary in
  length
• Predicted that some elements may not yet be
  discovered and left blank spots in the periodic
  table

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Henry Moseley 1913

• Worked with Ernest Rutherford
• Arranged the periodic table by atomic number
  (number of protons) instead of atomic mass
• Also noticed certain electron configurations are
  repeated periodically

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The Periodic Law

• The physical and chemical properties of the
  elements are a periodic function of their atomic
  numbers

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Arrangement of the Periodic Table

• Groups/Families
• Vertical columns
• Atoms in the same group have similar chemical
  properties
• Periods/Series
• Horizontal rows
• Indicates the highest principle quantum number
  (energy level)

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Metals

• Located to the left of the stairstep line
• Key Groups
• Alkali Metals (Group 1)
• Alkaline Earth Metals (Group 2)
• Transition Metals (Groups 3 12)
• Inner Transition Metals
• Lanthanide Series
• Actinide Series

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Metals

• Properties (at room temperature)
• Shiny (luster)
• Good conductors of heat and electricity
• Solids (except Hg)
• Can be bent, pulled into wires (ductile), or
  rolled into sheets (malleable)

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Nonmetals

• Located to the right of the stairstep line
• Key Groups
• Halogens (Group 17)
• Noble Gases (Group 18)
• Properties (at room temperature)
• Dull in appearance or glassy luster
• Poor conductors of heat and electricity
• Brittle
• Solids, liquids, and gases

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Metalloids

• Border the stairstep line
• Properties
• Share properties of metals and nonmetals
• Semiconductors
• Solids

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Periodic Trends

• Moving down a group
• Orbitals are larger
• Electrons are further from the nucleus
• Valence electrons are less tightly bound
  (electron shielding)
• Moving from left to right across a period
• More electrons are added to the same energy level
• The attractive force between the nucleus and the
  electrons increases (effective nuclear charge)
• Electrons are pulled closer to the nucleus
• Valence electrons are more tightly held

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Atomic Radius (Size)

• Atomic radius increases with increasing electron
  shielding
• Atomic radius decreases with increasing effective
  nuclear charge
• Cations have smaller radii than their neutral
  atoms
• Anions have larger radii than their neutral atoms

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Ionization Energy

• The energy necessary to remove an electron from
  an atom, molecule, or ion
• Ionization energy decreases moving down a group
  because of increased electron shielding
• Ionization energy increases moving left to right
  across a period because of increased effective
  nuclear charge

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Electronegativity

• The ability of an atom to attract an additional
  electron
• Electronegativity decreases moving down a group
  due to increasing electron shielding
• Electronegativity increases moving left to right
  across a period due to increasing effective
  nuclear charge

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Metallic/Nonmetallic Properties

• The most metallic elements are located on the far
  left of the periodic table
• The most nonmetallic elements are located on the
  far right of the periodic table
• Among metals, the metallic properties get
  stronger as you move down a group
• Among nonmetals, the nonmetallic properties get
  stronger as you move up a group