Ionic Bonding and Metallic Bonding

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Ionic Bondingand Metallic Bonding
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Keeping Track of Electrons

• The electrons responsible for the chemical
  properties of atoms are those in the outer energy
  level.
• Valence electrons - The s and p electrons in the
  outer energy level.
• Dealing with transition metals is a bit more
  complex, but we still mostly deal with s and p
  electrons first
• Core electrons -those in the energy levels below.

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Keeping Track of Electrons

• Atoms in the same column
• Have the same general outer electron
  configuration.
• Have the same valence electrons.
• Electrons can easily be found by looking up the
  group number on the periodic table.
• Group 2 - Be, Mg, Ca, etc.-
• 2 valence electrons

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Electron Dot diagrams

• A way of keeping track of valence electrons.
• How to write them
• Write the symbol.
• Put one dot for each valence electron
• Dont pair electrons up until there are no open
  spots left

X
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The Electron Dot diagram for Nitrogen

• Nitrogen has 5 valence electrons.
• First we write the symbol.

N

• Then add 1 electron at a time to each side.

• Until they are forced to pair up.

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Write the electron dot diagram for

• Na
• Mg
• C
• O
• F
• Ne
• He

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Electron Configurations for Cations

• Metals lose electrons to attain noble gas
  configuration.
• They make positive ions.
• If we look at electron configuration it makes
  sense.
• Na 1s22s22p63s1 - 1 valence electron
• Na 1s22s22p6 -noble gas configuration

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Electron Dots For Cations

• Metals will have few valence electrons

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• These will come off

Ca
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Electron Dots For Cations

• Metals will have few valence electrons
• These will come off
• Forming positive ions

Ca2
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Electron Configurations for Anions

• Nonmetals gain electrons to attain noble gas
  configuration.
• They make negative ions.
• If we look at electron configuration it makes
  sense.
• S 1s22s22p63s23p4 - 6 valence electrons
• S-2 1s22s22p63s23p6 -noble gas configuration.

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Electron Dots For Anions

• Nonmetals will have many valence electrons.

P
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Electron Dots For Anions

• Nonmetals will have many valence electrons.
• They will gain electrons to fill outer shell.

P
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Electron Dots For Anions

• Nonmetals will have many valence electrons.
• They will gain electrons to fill outer shell.
• Forming negative ions

P -3
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Stable Electron Configurations

• All atoms react to achieve noble gas
  configuration.
• Noble gases have 2 s and 6 p electrons.
• Again, we ignore the d electrons
• 8 valence electrons .
• This is called the octet rule.

Ar
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Stable Electron Configurations

• Which elements on the periodic table do not
  achieve a true octet when making stable,
  naturally occurring ions?
• H1, Li1, Be2, B3, H-1

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Ionic Bonding

• Anions and cations are held together by opposite
  charges.
• Attraction between opposite charges is called
  electrostatics
• Ionic compounds are called salts.
• Salts are what is left over when an acid and base
  react

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Ionic Bonding

• The simplest ratio of the atoms in an ionic
  compound is called the formula unit.
• Ionic bonds are formed through the transfer of
  electrons.
• Electrons are transferred to achieve noble gas
  configuration for both atoms/ions.

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Ionic Bonding
Na
Cl
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Ionic Bonding
Na
Cl
Electronegativity applies here. The chlorine has
a higher attraction to the electrons so . . .
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Ionic Bonding
Na
Cl
The electron is transferred to the chlorine
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Ionic Bonding
Na
Cl
The electron is transferred to the chlorine
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Ionic Bonding
Na
Cl-
Making the atoms into ions
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Ionic Bonding
Na
Cl-
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Ionic Bonding
Na
Cl-
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Ionic Bonding

• All the electrons must be accounted for!

Ca
P
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Ionic Bonding
Ca
P
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Ionic Bonding
Ca2
P
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Ionic Bonding
Ca2
P
Ca
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Ionic Bonding
Ca2
P-3
Ca
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Ionic Bonding
Ca2
P-3
Ca
P
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Ionic Bonding
Ca2
P-3
Ca2
P
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Ionic Bonding
Ca
Ca2
P-3
Ca2
P
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Ionic Bonding
Ca
Ca2
P-3
Ca2
P
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Ionic Bonding
Ca2
Ca2
P-3
Ca2
P-3
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Ionic Bonding
Ca3P2
Formula Unit
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Properties of Ionic Compounds

• They are formed as crystalline structure.
• A regular repeating arrangement of ions in the
  solid.
• Ions are strongly bonded (electrostatic
  attraction)
• Crystal structure is very rigid
• Ionic compounds have high melting points
• because of strong forces between ions.

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Crystalline structure
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Do they Conduct?

• Conducting electricity means charges are allowed
  to move.
• In a solid, the ions are locked in place
• No charges can move
• Ionic solids are excellent insulators

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Do they Conduct?

• Melting the compounds allows the ions to move
  freely.
• When melted the ions are no longer locked in
  place
• Separate ions can move
• Moving ions can conduct electricity
• Molten ionic compounds conduct electricity
• First get them to around 800ºC
• Then the ions have freedom of movement

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Do they Conduct?

• When dissolved water allows the ions to separate
• Separate ions can move
• Moving ions can conduct electricity

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Metallic Bonds

• How electrons are held together in the metallic
  solid
• Metals hold onto their valence electrons very
  loosely
• Due to a small electronegativity
• Electrons are not held in the valance shell
• Think of metals as positive ions floating in a
  sea of electrons

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Sea of Electrons

• Electrons are free to move through the solid
• Can metals conduct electricity?

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Metals are Malleable

• Hammered into shape (bend).
• Ductile - drawn into wires.

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Malleable
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Malleable

• Electron cloud allows ions to slide by

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Ionic solids are brittle
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Ionic solids are brittle

• Strong Repulsion breaks crystal apart.

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