Irvington High School  AP Chemistry
Mr. Markic
Name _______________________________
Number ___ Date ___/___/___
9  Basic Concepts of Chemical Bonding
Exceptions to
1.
the
Octet Rule
The AlI3 molecule has an incomplete octet around Al. Draw three resonance structures of the
molecule in which the octet rule is satisfied for both the Al and the I atoms. Show formal
charges
The resonance structures are
+
I

Al
I
I
I
+
I
I
I
2.

Al

Al
I
I
+
Of the noble gases, only Kr, Xe, and Rn are known to form a few compounds with O and/or F.
Write Lewis structures for the following molecules, in each case Xe is the central atom:
(a)
XeF2
(d)
XeOF4
(b)
XeF4
(c)
XeF6
(e)
XeO2F2
For simplicity, the three, nonbonding pairs of electrons around the fluorine atoms are omitted.
F
F
(a)
F
Xe
F
(b)
F
Xe
F
F
F
(c)
F
Xe
F
F
F
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O
O
F
(d)
F
F
Xe
(e)
F
F
Xe
F
O
The octet rule is exceeded in each case.
3.
Write Lewis structures for SeF4 and SeF6. Is the octet rule satisfied for Se?
For simplicity, the three, nonbonding pairs of electrons around the fluorine are omitted.
F
Se
F
F
F
F
Se
F
F
F
F
F
The octet rule is not satisfied for Se in both compounds (why not?).
4.
Write a Lewis structure for SbCl5. Does this molecule obey the octet rule?
The outer electron configuration of antimony is 5s25p3. The Lewis structure is shown below. All
five valence electrons are shared in the five covalent bonds. The octet rule is not obeyed. (The
electrons on the chlorine atoms have been omitted for clarity.)
Cl
Cl
Cl
Sb
Cl
Cl
Can Sb have an expanded octet?
5.
Write Lewis Structures for the reaction
AlCl3 + Cl-  AlCl4What kind of bond joins Al and Cl in the product?
The reaction can be represented as:
Cl
Cl
Al
Cl
+
Cl

Cl
Cl

Al
Cl
Cl
The new bond formed is called a coordinate covalent bond.
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