Periodic Trends

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Periodic Trends
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• Early Design
• Changes

• developed by Dmitri Mendeleev in the mid-1800s
• Organized elements by mass into rows and columns
• Found elements in the same column had similar
  properties
• Columns called
• Groups or Families

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• Electron Configurations

• Horizontal rows called periods
• Elements now arranged by atomic number (not mass)
• Elements in the same group have similar electron
  configurations
• 1st family all end in s1
• 2nd group all end in s2
• Etc.

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• Atomic Radius Trends

• Atoms on the left of a period are bigger than
  atoms on the right.
• Why?
• Electrons in same energy level
• Elements gain a proton each step to the right
• More protons more positive charge closer
  electrons

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• Atoms at the bottom of the table are bigger than
  atoms at the top.
• Why?
• Outermost electron level increases
• Electrons further away from nucleus
• An up/down move in the periodic table is a much
  more important change in atomic size than a
  left/right move.

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• Ionic Radius
• Ionic Radius Trends
• Ionic Radius Truths

• Distance from the nucleus to the outermost
  electron orbital
• Same periodic trends as neutral atoms
• Positive ions are always smaller than neutral
  atoms
• Why?
• Less electrons than protons greater pull toward
  nucleus

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• negative ions are always bigger than neutral
  atoms
• Why?
• More electrons than protons less pull toward
  nucleus

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• Ionization Energy
• Ionization Energy Trends

• The amount of energy required to remove an
  electron from an atom to make a positive ion.
• I.E. increases from left to right
• Why? More protons greater pull on the electrons
• I.E. Increases from bottom to top
• Why? Electrons closer to the nucleus

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• Electronegativity
• Electronegativity Trends

• The tendency for atoms of an element to attract
  electrons when they are chemically bonded to
  atoms of another element.
• How strongly they attract electrons
• The same as Ionization energy