Unit 2 – Chemical Bonding
Section 1 – Binding Forces
Bond Polarity and Electronegativity
1. What is electronegativity? The ability of an element to attract electrons.
2. What is the trend in electronegativity as you move from left to right
on the periodic table?
As you move from left to right, the electronegativity increases.
3. What is the trend in electronegativity as you move down a column
on the periodic table?
As you move down a column, the electronegativity decreases.
4. Arrange the bonds in each set in order of increasing polarity using
only the periodic table.
C—F, O—F, Be—F
C—S, B—F, N—O
O—F, C—F, Be—F
N—O, C—S, B—F
Ionic Bonding
5. Does the lattice energy of an ionic solid increase or decrease
a. As the charge of the ions increases? increase
b. As the size of the ions increases? decrease
6. The melting point of MgS is higher than KCl. Put an X next to the possible reasons.
a. __x__ Mg2+ is more positively charged than K+
b. _____ S2- is less electronegative than Clc. _____ The S2- ion is smaller than the Cl- ion
d. __x__ The Mg2+ ion is smaller than the K+ ion
7. Using only a periodic table, arrange the following substances from lowest to highest EXPECTED lattice energy:
ScN, KBr, MgO, NaF
KBr < NaF < MgO < ScN
First put them in order of increasing charge, if there is ever a tie,
use size to break the tie.
Covalent Bonding
8. Construct a Lewis structure for O2 in which each atom achieves an octet.
a. Why is it necessary to form a double bond in this structure? You need to satisfy the octet rule using the electrons
from the elements in the compound.
b.
Why is an O=O double bond shorter than and O—O single bond? In the double bond, more electrons are
being shared.
Additional Problems
9. Match the following descriptions of bonding to the different compounds below. Each description can be used
more than once.
a. Regular arrangement of positive and
 __a__ Strontium fluoride, SrF2(s)
negative ions held together by Coulombic
 __b__ Copper, Cu(s)
forces.
 __c__ Nitrogen, N2(g)
b. Positive ions with delocalized electrons
 __c__ Ethane, C2H6(g)
throughout
 __c__ Iodine, I2(s)
c. Strong covalent bonds with weak
 __a__ Nickel (II) chloride, NiCl2(s)
intermolecular forces.
 __b__ Magnesium, Mg(s)
10. Match the following types of bonding to the compounds below. Each type of bonding can be used more than
once.
a. Ionic bonding
 __b__ Methane, CH4(g)
b. Covalent bonding
 __b__ H2O(l)
c. Metallic bonding
 __b__ Nitrogen, N2(g)
 __c__ Nickel, Ni(s)
 __b__ PH3(l)
 __c__ Potassium, K(s)
 __a__ Sodium chloride, NaCl(s)