Characteristics of chemical bonds by pptfiles

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									Characteristics of chemical bonds
                     Metals
• What characteristic do metals have in common,
  as far as their desire to gain or lose electrons?
• Metals want to lose electrons
• Alkali metals: lose ___ electron
• 1
• Alkaline earth metals: lose ___ electrons
• 2
• This gives them a ____________ charge
• positive
                Non-metals
• What characteristic do non-metals have in
  common, as far as their desire to gain or lose
  electrons?
• Non-metals want to gain electrons
• This gives them a _________ charge
• negative
            Chemical Bonds
• Bond – a force that holds two or more atoms
  together and makes them function as a unit.
            Opposites attract
• When the negatively charged non-metals are
  attracted to the positively charged metals,
  they form an …
• ionic bond: the attraction between oppositely
  charged ions.
• These ionically bonded ions are called…
• ionic compounds: when a metal bonds with a
  non-metal
     Properties of ionic compounds
•   Very high melting and boiling points
•   Brittle solids
•   Solids don’t conduct electricity
•   Water soluble
•   Highly conductive once melted or dissolved
•   Solutions are good electrical conductors
               Bond Energy
• You can determine the amount of energy on a
  bond by testing how much energy it takes to
  break the bond.
• The amount of energy in a bond is called the…
• bond energy – duh!
    Bonding of Similarly Charged Ions
• Does hydrogen want to lose or gain electrons?
• Gain
• How many?
• 1
• When 2 hydrogen atoms get close enough to
  each other, they attract and “share” their one
  electron each, to give access to the other’s.
• The electrons move about both nuclei.
• The union that comes from atoms sharing
  electrons is called a Covalent bond
           Covalent bonding
• Draw the Lewis Dot structure of two hydrogen
  atoms bonded covalently
• How many electrons does each get the
  impression of having in its valence orbital?
• 2 electrons
• Draw 2 oxygen atoms bonded covalently
• How many electrons does each get the
  impression of having in its valence orbital?
• 8 electrons
• Are they “happy”?
         Polar Covalent Bonding
• Now draw the Lewis Dot structure for hydrogen and
  fluorine atoms bonding covalently
• Are they “happy” (full valence)?
• Do you think the hydrogen and fluorine nuclei have an
  equal attraction to the electrons?
• Which has more?
• Fluorine
• This is called polar covalent bonding:
• The electrons are not shared equally because one atom
  has a greater attraction to the shared electrons than
  the other.
        Polar Covalent Bonding
• The polarity of a bond depends on the
  difference between the electronegativity
  values of the atoms forming the bond.

								
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