Periodic Table Shortcut Noble Gas Notation Lewis Dot Structures

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Periodic Table ShortcutNoble Gas NotationLewis
Dot Structures
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When we write electron configurations, do we need
to always start at the beginning?

• No, there are a few shortcuts.

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The first shortcut involves the placements of
elements on the periodic table

• Let us look at the electron configurations from
  yesterdays homework and bell work from today and
  see how they fall on the periodic table.
• You will need 4 color pencils for this.

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So, the periodic table is arranged with electron
configurations in mind

• The only exception is He

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The rows and columns

• The rows correspond to the principle quantum
  number (n)
• In other words, each time you drop a row on the
  periodic table, you go out an energy level.
• Be careful with the d and f areas
• The d area is n-1 and the f area is n-2
• La and Ac are considered the first f area
  elements
• The sets of columns correspond to l quantum
  numbers and the amount of electrons in that
  orbital

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So, by looking at the periodic table, one can
find an elements electron configuration
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Lets try some examplesRemember it should be a
number then a letter then a superscript

• What is the last orbital of tin (Sn)?
• What is the last orbital of Ruthenium (Ru)?
• What is the last orbital of Holmium (Ho)?
• What element ends with the electron configuration
  of
• 5s1
• 6p4
• 5f3 (remember Ac is first f)

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The second shortcut

• We need to find a group of elements that have
  completed or full orbitals.
• That group is the noble gases.
• The last column on the periodic table.
• This group can be used to write an abbreviated
  version of an elements electron configuration.

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Lets look at yesterdays homework again
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How to write Noble Gas Notation

• Find the closest _________ noble gas to the
  element in atomic number without going over.
• Write that noble gass symbol in brackets.
• Go back to the beginning of the row and work back
  to the elements writing down the orbital sections
  and counting the electrons as you go.

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Examples

• As (Atomic Number 33)
• What is the closest Noble gas without going over?
• Ar
• So, Ar
• C
• He2s22p2
• Pb
• Xe

4s2
3d10
4p3
6s2
5d10
6p2
4f14
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Lewis Dot Formulas

• Shows the valence electrons of an atom
• Valence electrons are the electrons in the
  outermost energy level
• The only electrons that are in the outermost
  energy level are s and p.
• Therefore, the most valence electrons an atom can
  have is 8 (2 from the s and 6 from the p).

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Lewis Dot Formulas

• So, Lewis Dot Formulas are the chemical symbol
  surrounded by dots.
• There will be one dot per electron in the s and p
  orbital
• Hunds rule must be followed

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What is the Lewis Dot Structure for the following?

• Francium
• Arsenic
• Hydrogen
• Krypton
• Oxygen