Periodic Trends

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Periodic Trends

• Oh, theyre trendy alright

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How do Electron Configurations Figure in?

• Write the electron configurations for the
  following
• Li, Na Mg, Ca
• B, Al C, Si
• N, P O, S
• F, Cl Ne, Ar
• Now write the general configurations
• What kind of patterns do you notice?

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Valence Electrons

• Each group (or Family) has the same number of
  electrons in their outer most level
• Valence electrons Electrons in the outer most
  shell (or outer most level) of an atom
• Important because determine how reactive
  an element is (group 1 and group 17 (7A) are the
  most reactive metals and nonmetals, respectively)

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Valence Electrons

• What makes atoms happy?
• How many valence electrons do atoms want to have?
• Atoms want 8 valence electrons to be happy.
• There are 2 exceptions to this what are they?
• Why dont electrons completely fill the 3rd
  principal energy level before they start to fill
  the forth?

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Now to the trends Ionization Energy

• What is an ion ?
• an atom (or molecule) that has gained or lost
  electrons so that it now has a negative or
  positive charge
• So ionization energy is
• the energy needed to remove an electron from an
  atom

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Now to the trends Ionization Energy

• Increases as you move up a group
• As you move down a group there are more electrons
  in an atom, so there is electron shielding
  inner electrons shield the outer electrons from
  the attractive force of the nucleus
• Increases as you move across (to the right) a
  period
• Compare Na and Cl - which one has closer to the
  magic number of valence e- ?
• So it will be harder to take an e- from which
  atom?

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Now to the trends Atomic Radius

• What do you think the trend for this will be?
• Increases down a group
• Increases going LEFT across a period

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Now to the trends Electronegativity

• Electronegativity
• a measure of the ability of an atom to attract
  an electron
• Which atom wants an electron more?
• Trend
• increases going up a group
• increases going right across a period
• Why?

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• Homework Trends in the Periodic Table Wksht
• Corresponding Reading
• Textbook Chapter 4 - Section 3
• Pages 132 - 141