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					 Bellwork:

Which of the following concepts underlies all the others:
ionization energy, effective nuclear charge, atomic size?
Use at least three sentences to explain your answer.




 Effective nuclear charge gives rise to the properties
 of ionization energy and atomic size. The larger the
 effective nuclear charge, the smaller the atom is
 going to be. The larger the effective nuclear
 charge, the greater the ionization energy will be.
Ch. 6 & 7 - Chemical Bonding



     I. Introduction to
           Bonding
         (p. 161 – 163)
                  OBJECTIVES
2.4.1   Define chemical bond

2.4.2   Explain why most atoms form chemical bonds.

2.4.3   Describe ionic and covalent bonding.

2.4.4   Classify bonding type according to electronegativity
        differences

2.4.5 Define molecule and molecular formula.
Vocabulary

Chemical Bond
 electrical attraction between nuclei and
  valence e- of neighboring atoms that
  binds the atoms together
 bonds form in order to…
  decrease PE
  increase stability
Vocabulary



Octet Rule:
Atoms will transfer or share electrons in order to have
8 electrons in their highest energy level.
   •   This makes it like a noble gas
  Types of Bonds
                       IONIC                 COVALENT
Bond            e- are transferred from   e- are shared between
Formation          metal to nonmetal          two nonmetals
Type of
                    crystal lattice          true molecules
Structure
Physical
State                    solid                liquid or gas
Melting
                         high                     low
Point
Solubility in
                          yes                  usually not
Water
Electrical                yes
Conductivity      (solution or liquid)             no
Other
Properties
Types of Bonds
                      METALLIC
    Bond             e- are delocalized
    Formation       among metal atoms
    Type of
                      “electron sea”
    Structure
    Physical
                          solid
    State
    Melting              very high
    Point
    Solubility in           no
    Water
    Electrical             yes
    Conductivity        (any form)
    Other           malleable, ductile,
    Properties           lustrous
Quick Hint
All covalent bonds are between
two non-metals

All ionic bonds are between a
metal (cation) and a nonmetal (anion).

All metallic bonds are between
two metals
Vocabulary

   CHEMICAL FORMULA

  IONIC         COVALENT


  Formula     Molecular
    Unit      Formula


  NaCl         CO2
Vocabulary

          COMPOUND
                 more than 2
 2 elements
                  elements

   Binary        Ternary
 Compound       Compound


  NaCl          NaNO3
Vocabulary

             ION
   1 atom          2 or more atoms


Monatomic          Polyatomic
   Ion                 Ion


  Na+               NO3-
Bond Polarity

Most bonds are
 a blend of ionic
 and covalent
 characteristics.
Bond Polarity

Nonpolar Covalent Bond
 e- are shared equally
 symmetrical e- density
 usually identical atoms
Bond Polarity

Polar Covalent Bond
 e- are shared unequally
 asymmetrical e- density
 results in partial charges (dipole)




 +                                 -
Bond Polarity

Ionic Bond
 e- are not shared
 results in charged particles
 opposite charges attract
Bond Polarity

Electronegativity
 Attraction an atom has for a shared pair
  of electrons.
 higher e-neg atom  -
 lower e-neg atom +
Bond Polarity

Electronegativity Trend (p. 151)
 Increases up and to the right.
Bond Polarity

Difference in the
 elements’ e-negs
 determines bond
 type
Determining Type, DEN
 0.3           1.7



  5%           50%
   Determining Type, DEN




Ionic, Polar or Nonpolar Covalent Compounds: The difference
in electronegativity between bonding atoms leads to the type of compound.

Example:
O2 , O=O        ENO = 3.5                D EN = 0      g   Nonpolar Covalent
NO , N=O        ENN = 3.0, ENO = 3.5     D EN = .5     g   Polar Covalent
CO , C= O       ENC = 2.5, ENO = 3.5     D EN = 1.0    g   Polar Covalent
NaCl , Na+Cl-   ENNa = 0.9, ENCl = 3.0   D EN = 2.1    g   Ionic
   Sample Problem 6-1
Use electronegativity differences to classify bonding between
sulfur, S, and the following elements: hydrogen, H; cesium, Cs; and
chlorine, Cl. In each pair, which atom will be more negative?
Bonding
between       Electronegativity                     More-negative
sulfur and    difference           Bond type        atom

hydrogen       2.5 – 2.1 = 0.4    Polar-covalent     sulfur
cesium         2.5 – 0.7 = 1.8    Ionic              sulfur
chlorine       3.0 – 2.5 = 0.5    Polar-covalent     chlorine
  Additional Sample Problems
Complete the following chart:
Elements
bonded         Electronegativity                       More-negative
               difference          Bond type           atom

a. C and H     2.5 – 2.1 = 0.4     Polar-covalent       carbon
b. C and S     2.5 – 2.5 = 0       Nonpolar covalent    Same electronegativity
c. O and H     3.5 – 2.1 = 1.4     Polar-covalent       oxygen
d. Na and Cl   3.0 – 0.9 = 2.1     Ionic                chlorine
e. Cs and S    2.5 – 0.7 = 1.8     Ionic                sulfur
                 Homework

HW 6-1
 pg. 195 #1-5, 33-34
    Due: Tu 10/30

				
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