Periodic Trends

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Section 5-3

• Periodic Trends

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Atomic Radius

• Distance from the center of the atoms nucleus to
  the outermost electrons.
• 1. Atoms get larger going down a group.
• More energy levels
• 2. Atoms get smaller moving from left to right.
• Atoms have more protons as you move from left to
  right.
• Therefore, the nucleus has a greater pull on the
  electrons.

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Atomic Radius Trend
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Ionization Energy

• The energy needed to remove one of an atoms
  electrons.
• How strong does an atom hold its electrons?
• 1. Decrease as you move down a group
• The smaller the atom the easier it is for the
  nucleus to hold onto its electrons.
• Shielding effect electrons in lower energy
  levels shields the outer electrons from the
  effects of the nucleus

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Ionization Energy cont.

• 2. Increase as you move from left to right
  across a period.
• More valence electrons (closer to fulfilling the
  octet rule)

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Electronegativity

• The ability to attract to attract electrons in a
  chemical bond
• 1. Decrease as you move down a group
• 2. Usually increase across a period
• Exclude noble gases (do not form bond.)
• Most electronegative element Fluorine
• Least electronegative element - Francium

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Electronegativity Trend
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Ionic Size

• Ions are atoms that have gained or lost electrons
• Positive ion becomes smaller
• Negative ion becomes larger
• Electron Affinity the energy change that occurs
  when it gains an extra electron.