Lewis Dot Diagrams

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Lewis Dot Diagrams

• Mrs. Kay

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Energy in the atom

• Charged particles called electrons surround the
  nucleus in regions called shells or energy levels

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• Atoms of different elements have different
  numbers of electrons
• Each shell is full before electrons move to the
  next shell.

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• Period number number of electron shells
• Shells will fill in the following order 2, 8,
  8,18
• Group number number of valence electrons (look
  at the second digit of the group number)

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Trends

• Elements of the same group have similar
  properties because they have the same number of
  electrons in their outer shell.
• The outer shell valence shell
• Electrons that occupy the valence shell are
  called valence electrons

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Noble gas configuration

• Group 18, the noble gases are the most stable of
  elements because their valence shell is full with
  electrons
• Less energy required
• Stable octet

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Lewis Dot diagrams

• Visual representation of an element and only its
  valence electrons
• Example sodium, Na has one valence so it has 1
  dot representing that electron.
• Chlorine has 7 electrons.
• Electrons get paired up along 4 sides of the
  element.

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Bonding

• Ionic bonding attraction between oppositely
  charged ions formed when metallic ions ()
  transfer electron(s) to nonmetallic ions (-)
• Ex NaCl

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• Not always 11 ratio, sometimes need to use
  subscript to show the number of atoms
• Ex CaCl2 The 2 is a subscript, it shows that 2
  atoms of chlorine bond with one atom of calcium.
• The charges need to have a sum of zero

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Covalent / Molecular bonding

• Formed when a pair of electrons is shared by two
  non-metal atoms.
• A single bond is formed when one pair of
  electrons is shared.
• Example diatomic molecules, like O2, H2, N2,
  F2, Cl2

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Single bonds
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Polar Covalent Bonding

• Electrons are shared unequally.
• They are not ionic, because the electron is not
  totally removed because there was not enough
  attraction to totally remove the electron.

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Polar covalent bond
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• When you have a polar covalent bond, one atom
  will attract an electron closer than the other.
• Called polar molecules because one end is
  slightly positive and one end is slightly negative

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Water is Polar!

• Water is very common polar compound.
• The hydrogen are slightly positive (because
  almost gave up e-)
• The oxygen is slightly negative (because almost
  took the e-)

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Naming Compounds the rules!

• Mrs. Kay

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1st What are polyatomic ions?

• Ions that are made of multiple atoms covalently
  bonded together.
• We treat them like a unit
• Example sulfate, SO4-2 so sulfur and oxygen
  form a negative ion (-2)

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Given the Formula Fe2(SO4)3

• Step One The cation is always the first thing
  you see in the name, and the anion is always the
  second thing. In this case, you should recognize
  that Fe is "iron", and that SO4 is the "sulfate"
  ion. Generally, if one of these ions has more
  than one atom in it, you'll need to look it up in
  a chart.
• you need to know eight of the polyatomic ions
  hydroxide, nitrate, nitrite, sulfate, sulfite,
  carbonate, phosphate, ammonium.

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• Step Two Figure out if you need a Roman numeral
  in the name. If the cation in the compound
  you're naming is not a transition metal (group
  3-12), then you definitely don't need to use a
  Roman numeral and the naming is done. If there
  is, then you need to figure out whether or not
  the cation can exist in more than one charge. If
  not, then you don't need a Roman numeral. If so,
  then move on to Step Three...

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• Step Three Figure out what the Roman numeral
  should be Basically, this should be fairly easy.
  A good rule of thumb is that usually the number
  of anions you have in the molecule is equal to
  the charge on the cation, and that the number of
  cations you have is equal to the number of
  anions. Using our example, there are three
  sulfate ions, meaning that iron has a charge of
  3. Likewise, since there are two iron atoms, the
  sulfate has a charge of -2. Since iron has a
  charge of 3 in this compound, the name in this
  example is iron (III) sulfate

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Given the name, find the formula

• Step One Translate the name into the ions In
  copper (II) fluoride, the cation is the copper
  (II) ion and the anion is the fluoride ion.
  Hopefully, you realize that the copper (II) ion
  is simply Cu2 and the fluoride ion is F-. If
  not, then you need to go back and review the
  rules for naming ions above.

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• Step Two Put brackets around the ions, but leave
  the charges on the outside. In this case, the
  copper (II) ion would be Cu2 and the fluoride
  ion would be F-1. Never change anything in
  these brackets, ever!
• Step Three Put the ions next to each other.
  When we do this here, we get Cu2F-1

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• Step Four Cross the charges The charge on the
  cation will be equal to the number of anions you
  have, and the charge on the anion will be equal
  to the number of cations you have. In our
  example, you should realize that we have one
  copper atom (because the charge on fluorine is
  -1) and two fluoride ions (because the charge on
  copper is 2). This gives us a formula of
  CuF2
• Step Five Take the brackets away. The final
  formula for copper (II) fluoride is then CuF2

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Naming Covalent compounds

• All covalent compounds have two word names.  The
  first word typically corresponds to the first
  element in the formula and the second corresponds
  to the second element in the formula except that
  "-ide" is substituted for the end.  As a result,
  HF is named "hydrogen fluoride", because hydrogen
  is the first element and fluorine is the second
  element

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If there is more than one atom of an element in a
molecule, we need to add prefixes to these words
to tell us how many are present.  Here are the
prefixes you'll need to remember

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Test what you know herehttp//science.widener.ed
u/svb/tutorial/namingcsn7.html