Periodicity

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Periodicity

• Trends in the Periodic Table

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Atomic Radius

• One half the distance between nuclei of identical
  atoms that are bonded together
• Decrease across a period due to increasing
  positive nuclear charge
• Increase down a group due to increasing number of
  energy levels (outer electrons are farther from
  the nucleus)

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Ionization Energy

• Ion An atom or group of atoms that has a
  positive (cation) or negative (anion) charge
• Ionization The formation of an ion
• Ionization Energy The energy required to remove
  one electron from a neutral atom of an element,
  measured in kilojoules/mole (kj/mol)

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Ionization Energy

• IE increases for each successive electron
• Each electron removed experiences a stronger
  effective nuclear charge
• Greatest increase in IE comes when trying to
  remove an electron from a stable, noble gas
  configuration.

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Ionization Energy

• IE tends to increase across each period.
• Atoms are getting smaller, electrons are closer
  to the nucleus
• IE tends to decrease down a group
• Atoms are getting larger, electrons are farther
  from the nucleus
• Outer electrons becomes increasingly more
  shielded from the nucleus by inner electrons
• Metals have characteristically low IE
• Nonmentals have high IE
• Noble gases have a very high IE

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Ionic Radius

• Cations have a smaller ionic radius than
  corresponding atom
• Protons outnumber electrons
• Less shielding of electrons
• Anions have a larger ionic radius than
  corresponding atom
• Electrons outnumber protons
• Greater electron-electron repulsion

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Electron Affinity

• Energy change that occurs when an atom accepts an
  electron
• Halogens have the highest electron affinities
• Metals have low electron affinities
• Affinity tends to increase across a period and
  decrease down a group

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Electronegativity

• The ability of an atom to attract electrons when
  bonded
• Nonmetals have high electronegativity
• Metals have low electronegativity
• Electronegativity increases across a period and
  decreases down a group

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Electronegativity
Electronegativity