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Ionic Bonding

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					CHEMISTRY

October 19th, 2011
               Welcome Back!
                        th
              October 19 , 2011
•    Brainteaser:
    – Let’s reflect on last quarter’s performance:
    – What are some things you thought you did
      well for this class?
    – What are some things you think you could
      improve for this quarter?
    – What is your overall goal for this quarter (i.e.
      what do you want to accomplish this quarter
      and how are you going to do it?)
                 Agenda
• Brainteaser
• Unit 5: Ionic Bonding Notes
• Homework
  – Ionic Bonding Practice Worksheet
    Unit 4: Chemical Bonding
• Bonding
  – Differences in chemical behavior are due to
    differences in the types of bonds
  – Bond: forces that hold atoms together in
    molecules or ionic compounds.
            Chemical Bonding
• Types of bonds and types of
  substances

  – Ionic

  – Covalent

   – Metallic
• The type of bond between atoms is partially
  responsible for the properties of the
  substance.
            Chemical Bonding
• Bonding
  – Involves the valence electrons or outermost shell (or
    highest shell) electrons
  – For group A elements – the group number tells how
    many valence electrons
     • For example:
        – K, Ca, C, B, N, F, Ne
  – Lewis Dot Structures show the valence electrons
    around an atom and for most molecules and
    compounds a complete octet for the elements is
    needed.
     • For example: N, Al, H2O
        Lewis Dot Structures

• These symbols are
  called Lewis symbols à
• We generally place the
  electrons on four sides
  of a square around the
  element symbol.
  Drawing Lewis Dot Structure
• Place DOTS around the SYMBOL
  clockwise pairing up dots on the second
  time around
  – For example:
    • Magnesium (Mg) and Oxygen (O) à MgO

     Mg

     O
Ionic Bonding
   Ions and Ionic Compounds
• Ions are formed by adding or subtracting
  electrons from a neutral atom or molecule.
• Cation: positively charged ions (remove e-)
• Anions: negatively charged ions (add e-)

• Names!!
        Two Types of Ions
• Monatomic ions
  – Single atom ions
    • O 2-
    • Na+
    • Al3+
• Polyatomic ions
  – More than one atom ions
    • NH4 +
    • OH –
    • SO4 2-
    Predicting Charges of Ions
• Electron Counts of Stable Ions
   – Ions tend to have the same number of
     electrons as the nearest noble gas.
• Transition metals are not as predictable, but +2
  and +3 are common.
              Main Group Elements


Note
periodicity
of charges
   Transition Elements
• Not periodic; +2 and +3 common
      Charges and Formulas of
            Oxoanions
• Oxoanions generally have the same
   charge as the simple anion of the same
   nonmetal.
  Related to
  position in
  the periodic
 Polyatomic Ions
  table; note
  exceptions
 tend to reflect
  for B, C, of
 the charge N the
base element
    Ionic Bonds form when…
• A cation (metal) bonds with an anion
  (nonmetal)
• A salt is formed:
  – For example: Sodium: Na “metal” bonded to
    Chlorine: Cl “nonmetal”
  – For example: Magnesium: Mg “metal” bonded
    to Chlorine: Cl “nonmetal”
        Ionic Bonding:
The Formation of Sodium Chloride

q Sodium has 1 valence electron
q Chlorine has 7 valence electrons

q An electron transferred gives
  each an octet
      Na: 1s22s22p63s1
    Cl: 1s 2s 2p 3s 3p
         2   2   6   2   5
        Ionic Bonding:
The Formation of Sodium Chloride
 This transfer forms ions, each
 with an octet:
         Na 1s 2s 2p
            +   2   2   6


          Cl- 1s22s22p63s23p6
The resulting ions come together
due to electrostatic attraction
     (opposites attract):

           Na +
           Na Cl  Cl -

The net charge on the compound
must equal zero
         Lewis Dot Drawing
• Ionic bond    • A positively charged ion is
                  attracted to a negatively
                  charged ion.
                • A transfer of electrons
                • Metal and a Non-Metal

• Example       • NaCl
  – Lewis Dot
    diagram
                   Na     Cl       Na Cl
                Practice
• Draw the Lewis dot structures for the
  following compounds:
  – CaO
  – BaCl2
  – Na2S
        Writing Formulas for Ionic
               Compounds
• Crisscross   • Write the element symbols for the
  Method         cation and anion, with the cation on
                 the left and the anion on the right.
               • Write each ion’s charge as a
                 superscript.
               • Crisscross the two charges moving
• Example:
                 them downward diagonally from
   Ca and F
                 one superscript to the other
                 subscript.
                 Practice
• Write the correct formula for the ionic
  compounds composed of the following
  pairs of ions using the crisscross method:
  – Potassium and iodide
  – Magnesium and chloride
  – Aluminum and bromide
  – Cesium and nitride
  – Barium and sulfide
  – Iron (II) and fluoride
CHEMISTRY

October 20th, 2011
                Warm Up
• Write the correct formula for these ionic
  compounds:
  – Aluminum oxide
  – Barium nitride
  – Iron (III) oxide
  – Magnesium carbide
                   Agenda
• Brainteaser
• Grade Homework: Practice W/S
• Unit 5 Notes:
  – Naming Ionic Compounds
  – Properties of Ionic Compounds
• Partner Bonding Activity
• Homework:
  – Naming Ionic bonds W/S
      Naming Ionic Compounds
• Step 1:
   – Cation is written first in the name; anion is written second in the
     name
       • Name of cation is the same as the neutral atom element
         (Na+ = Sodium)
• Step 2:
   – Anion is written by adding the suffix –ide to the root of the
     element name (I- = iodide)
       • For example: NaCl = Sodium Chloride, Al2O3 = Aluminum oxide
• Step 3:
   – Figure out if you need a Roman numeral in the name (transition
     metals).
       • Figure out what the Roman numeral should be
            – For example: Fe2O3
• Step Four: Check your work
               Practice
       Naming Ionic Compounds
•   KF
•   AlF3
•   KCl
•   Na3P
•   Fe2O3
    Properties of Ionic Bonding
• Definition:
  – In an ionic bond, a positively charged ion is
    attracted to a negatively charged ion
     • Electrostatic Attraction
    Properties of Ionic Bonding
• Solid at room temperature
• Electrical conductivity
  – Conducts electricity when dissolved in water or in liquid
    (molten) form
  – Dissociated ions can carry charge through the solution
• Hardness
  – Hard but brittle
  – Electrostatic repulsion
• Melting points and Boiling points
  – High melting and boiling point
  – Forces of attraction between positive and negative ions
    are strong
Properties of Ionic Bonding
                   Quiz
• Write the chemical formula for these ionic
  compounds:
  – Sodium bromide
  – Potassium nitride
  – Beryllium phosphide
• Write the chemical names for these ionic
  compounds
  – SrCl2
  – MgI2
  – Ba3N2

				
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