PERIODIC TRENDS

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PERIODIC TRENDS

• Atomic size
• Ionization energy

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Atomic Size

• For the main group elements (s p blocks),
  atomic radii increase going down a group and
  decrease from left to right across a period.

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Putting Trend to Use

• Using the periodic table, arrange the following
  in order of increasing atomic radius
• Br, Te, Se

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Ionization energy, IE, is the amount of
energy required to remove an electron from an
isolated, gas phase atom.

• Energy is always required for this process.
• IE generally decreases going down a group
• and generally increases from left to right
• across a period.

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Electron Affinity

• Energy released when a lone, gaseous atom gains
  an electron.
• F e- ? F-

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Electron Affinity, EA, is the amount of energy
released when a free, gas phase atom gains an
electron.
EA increases (i.e., more energy is released) as
we move to the top and right of the periodic
table.
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Ionic Size

• All positive ions are smaller than the atoms from
  which they were formed
• All negative ions are larger than the atoms from
  which they were formed.