Lewis Dot Structures and Electrons

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Lewis Dot Structures and Electrons

• Ms. Daniels
• Brighton Collegiate High School
• Chemistry

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What are Lewis (Dot) Structures?

• They show the valence electrons as dots around
  the element symbol.
• They can also show the bonds between atoms of a
  molecule and any unbonded electron pairs.
• Named after Gilbert Lewis who described them in a
  1916 article titled The Atom and the Molecule.

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What are valence electrons?

• These are the electrons in the highest energy
  level/outer-most electron orbital.
• The valence electrons largely determine the
  chemical properties of an element
• The number of valence electrons is also related
  to the group numbers on the periodic table.
• The valence electrons are used in bonding too!

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Group A elements and Valence Electrons

• Group 1A 1 valence electron
• Group 2A 2 valence electrons
• Group 3A 3 valence electrons
• Group 4A 4 valence electrons
• Group 5A 5 valence electrons
• Group 6A 6 valence electrons
• Group 7A 7 valence electrons
• Group 8A 8 valence electrons
• A little redundant I know!

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What are the rules for writing Lewis Structures?

• Pick the central atom by writing its element
  symbol. The central atom is the one with the
  lowest electronegativity.
• Typically increases from left to right on P.T and
  from the bottom up to the top.
• Whats electronegativity? It is the tendency for
  an atom to attract electrons to itself when
  bonding with another element.

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More rules for writing Lewis Structures

• You must fill in the dots around an element 1 at
  a time.
• Example 1 dot east of an element, then 1 dot west
  of an element, then 1 dot south of an element,
  then 1 dot north of an element.
• Another example is on the board

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Lets try some examples

• Write what you think the Lewis structure will
  look like for the following elements
• H
• He
• Li
• B
• C
• N
• O
• F
• Ne

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How does this relate to bonding?

• The valence electrons are useful in helping you
  visualize how many electrons there are in an
  element and how many it needs to bond with.
• Remember all atoms like to have 8 valence
  electrons in their outer-most orbital!
• We will talk more about bonding next!!!!