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Why Do Atoms Bonds with each
other?
Bonding and Stability
   An atom becomes more
    stable when it acquires
    the electron
    configuration of a noble
    gas

   Two for the 1st principal
    energy level and eight
    for the others.

   The Octate Rule

   As any system become
    more stable, its energy
    decreases
IONIC BONDING
IONIC BONDING
   To achieve noble gas configuration, a pair of
    atoms may fill their valence level by transferring
    electrons between them to form ions with
    opposite charges.
   The opposite charges cause them to attract
    strongly, forming this type of bond.
     IONIC BONDING
   The attraction is not
    limited to pairs of ions.
   Oppositely charged ions
    arrange themselves in a
    regular array.
   The formula tells us the
    ratio of positive to
    negative ions- The
    Formula Unit.
   Eg. In the case of NaCl,
    the ratio is 1 to 1
IONIC BONDING What is necessary for electron
transfer to occur?


   One atom must be       Low
    able to lose
    electron readily
                            Ionization
                            Energy
   The other atom
    must be able to
                           Negative
    gain electrons
    readily                 Electron
                            Affinity
COVALENT BONDING
      COVALENT BONDING
   Some pairs of atoms
    do not have a strong
    tendency to transfer
    electrons between
    them.
   These atoms SHARE
    electrons between
    them.
   Two atoms may
    normally share one,
    two, or three pairs of
    electrons.
   The atoms bond
    together because the
    shared pair or pairs
    belonging to both
    atoms
         COVALENT BONDING
Single Covalent bond

   Each molecule a
    single pair of
    electrons is shared
    between the
    atoms.

   F—F and H--Cl
    COVALENT BONDING The sharing of the
    electrons is not always equal between both atoms.


    Nonpolar                          Polar Covalent
     Covalent
                          The electron pair is not
The pair of                 shared equally; the
  electrons is              chlorine atom has a
  shared equally            greater attraction for the
  by both atoms             shared electrons than the
                            hydrogen atom.
        F--F
                                             H--Cl
Multiple Covalent Bonds
   Create the electron dot symbol for oxygen.
   Construct a molecule of O2.
   In order to place eight electrons in the valence level of
    each oxygen atom it is necessary that the atom share
    two pairs of electrons
   This is known as double covalent bonds.
    Multiple Covalent Bonds
   How is a molecule of N2 constructed?
   Nitrogen has five valence electrons
   It is necessary that the two atoms share three pairs of
    electrons
   This is known as a triple covalent bond.
     Coordinate Covalent Bonding
   Draw the Lewis structure for NH3.
   Add a H+ ion to form the ammonium ion (NH4+)
   The hydrogen ion lacks electrons; and when it
    bonds the nitrogen atom must contribute both
    electrons to the shared pair.
   This type of bond is found in many molecules and
    polyatomic ions.

				
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