1. Compounds and Their Bonds
Electronegativity and Bond Polarity
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2. Electronegativity The electronegativity value
indicates the attraction of an atom for shared electrons.
increases from left to right going across a period on the periodic table.
is high for the nonmetals with fluorine as the highest.
is low for the metals.

3. Some Electronegativity Values for Group A Elements
Electronegativity decreases `
Electronegativity increases
High values `
Low values
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4. Elements with a HIGH electronegativity have a STRONG pull on electrons.
Elements with a LOW electronegativity have a WEAK pull on electrons.

5. difference in electronegativity.
A large difference in electronegativity means one atom will win the “tug of war” and take the electrons completely.
This is an ionic bond.

6. When the electronegativity of two bonding atoms is very similar,
neither atom wins the “tug of war” and the electrons are shared equally.
This produces a covalent bond

7. Nonpolar Covalent Bonds
A nonpolar covalent bond
occurs between nonmetals.
is an equal or almost equal sharing of electrons.
has almost no electronegativity difference (0.0 to 0.4).
Examples:
Electronegativity
Atoms Difference Type of Bond
N-N = Nonpolar covalent
Cl-Br = Nonpolar covalent
H-Si = Nonpolar covalent

8. Polar Covalent Bonds A polar covalent bond
occurs between nonmetal atoms.
is an unequal sharing of electrons.
has a moderate electronegativity difference (0.5 to 1.7).
Examples:
Electronegativity
Atoms Difference Type of Bond
O-Cl = 0.5 Polar covalent
Cl-C = 0.5 Polar covalent
O-S = 1.0 Polar covalent

9. Comparing Nonpolar and Polar Covalent Bonds
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Publishing as Benjamin Cummings

10. Ionic Bonds An ionic bond occurs between metal and nonmetal ions.
is a result of electron transfer.
has a large electronegativity difference (1.8 or more).
Examples:
Electronegativity
Atoms Difference Type of Bond
Cl-K – 0.8 = Ionic
N-Na 3.0 – = Ionic
S-Cs 2.5 – 0.7 = Ionic

11. Electronegativity and Bond Types
TABLE 4.14

12. Predicting Bond Types
Table 4.15

13. Rules for predicting bond type:
A bond between two atoms of the same element or between atoms having the same electronegativity value is a non polar covalent bond.
A covalent bond between atoms of two different nonmetals having different electronegativities is a polar covalent bond
A bond between a metal and a nonmetal is usually an ionic bond.