Irvington High School  AP Chemistry
Mr. Markic
Name _______________________________
Number ___ Date ___/___/___
9  Basic Concepts of Chemical Bonding
Electronegativity and
Bond Type
1. List the following bonds in order of increasing ionic character: the lithium-to-fluoride bond in LiF,
the potassium-to-oxygen bind in K2O, the nitrogen-to-nitrogen bind in N2, the sulfur-to-oxygen
bond in SO2, the chlorine-to-fluorine bond in ClF3.
The degree of ionic character in a bond is a function of the difference in electronegativity between
the two bonded atoms. Figure 9.5 lists electronegativity values of the elements. The bonds in order
of increasing ionic character are: NN (zero difference in electronegativity) < SO (difference 1.0) 
ClF (difference 1.0) < KO (difference 2.7) < LiF (difference 3.0).
2. Four atoms are arbitrarily labeled D, E, F, and G. Their electronegativities are as follows: D = 3.8,
E = 3.3, F = 2.8, and G = 1.3. If the atoms of these elements form the molecules DE, DG, EG, and
DF, how would you arrange these molecules in order of increasing covalent bond character?
We calculate the electronegativity differences for each pair of atoms:
DE: 3.8  3.3  0.5
DG: 3.8  1.3  2.5
EG: 3.3  1.3  2.0
DF: 3.8  2.8  1.0
The order of increasing covalent bond character is: DG < EG < DF < DE
3. List the following bonds in order of increasing ionic character: cesium to fluorine, chlorine to
chlorine, bromine to chlorine, silicon to carbon.
The order of increasing ionic character is:
ClCl (zero difference in electronegativity) < BrCl (difference 0.2) < SiC (difference 0.7)
< CsF (difference 3.3).
4. Classify the following bonds as ionic, polar covalent, or covalent, and give your reasons:
a. The CC bond in H3CCH3
(a)
The two carbon atoms are the same. The bond is covalent.
b. The KI bond in KI
(b) The electronegativity difference between K and I is 2.5  0.8  1.7. The bond is polar covalent.
c. The NB bond in H3NBCl3
(c) The electronegativity difference between N and B is 3.0  2.0  1.0. The bond is polar covalent.
d. The CF bond in CF4
(d)
The electronegativity difference between C and F is 4.0  2.5  1.5. The bond is polar covalent.
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