Skip to main content
Pearson+ LogoPearson+ Logo
Ch.8 - Basic Concepts of Chemical Bonding
All textbooksBrown 15th EditionCh.8 - Basic Concepts of Chemical BondingProblem 65
Chapter 8, Problem 65

Draw the Lewis structures for each of the following ions or molecules. Identify those in which the octet rule is not obeyed; state which atom in each compound does not follow the octet rule; and state, for those atoms, how many electrons surround them: (a) HCl, (b) ICl5, (c) NO, (d) CF2Cl2, (e) I3-.

Verified step by step guidance
1
Step 1: Begin by determining the total number of valence electrons for each molecule or ion. For neutral molecules, sum the valence electrons of all atoms. For ions, adjust the total by adding electrons for negative charges or subtracting for positive charges.
Step 2: Draw the skeletal structure of each molecule or ion, connecting atoms with single bonds. Typically, the least electronegative atom is placed in the center, except for hydrogen, which is always terminal.
Step 3: Distribute the remaining valence electrons as lone pairs, starting with the outer atoms, to satisfy the octet rule (or duet for hydrogen). If electrons remain, place them on the central atom.
Step 4: Check each structure to see if the octet rule is satisfied for each atom. Identify any exceptions to the octet rule, such as molecules with an odd number of electrons, atoms with less than an octet, or atoms with more than an octet (expanded octet).
Step 5: For each exception identified, specify which atom does not follow the octet rule and count the number of electrons surrounding it.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds between atoms. Understanding how to draw these structures is essential for visualizing molecular geometry and predicting reactivity.
Recommended video:
Guided course
04:28
Lewis Dot Structures: Ions

Octet Rule

The octet rule is a chemical rule of thumb that states atoms tend to bond in such a way that they each have eight electrons in their valence shell, achieving a stable electron configuration similar to that of noble gases. However, there are exceptions to this rule, particularly for elements in periods greater than two and for certain ions and molecules.
Recommended video:
Guided course
01:27
Octet Rule

Exceptions to the Octet Rule

Certain atoms can have fewer or more than eight electrons in their valence shell, leading to exceptions to the octet rule. For example, elements like hydrogen and helium are stable with two electrons, while elements like phosphorus and sulfur can expand their octet to accommodate more than eight electrons. Identifying these exceptions is crucial for accurately interpreting Lewis structures.
Recommended video:
Guided course
01:27
Octet Rule
Related Practice
Textbook Question

Which of the following statements about benzene, C6H6, is or are true?

i. Benzene has two equivalent resonance structures.

ii. There are no nonbonding pairs in the Lewis structure for benzene.

iii. Benzene has three short and three long C—C bonds.

Textbook Question

b. Which of these compounds or ions is an exception to the octet rule: nitrogen dioxide, borohydride (BH4−), borazine (B3N3H6 which is analogous to benzene with alternating B and N in the ring), or boron trichloride?

Textbook Question

Draw the Lewis structures for each of the following molecules or ions. Identify instances where the octet rule is not obeyed; state which atom in each compound does not follow the octet rule; and state how many electrons surround these atoms: a. NO, b. BF3, c. ICl2−, d. OPBr3 (the P is the central atom), e. XeF4.

Textbook Question

In the vapor phase, BeCl2 exists as a discrete molecule. (a) Draw the Lewis structure of this molecule, using only single bonds. Does this Lewis structure satisfy the octet rule?

Textbook Question

In the vapor phase, BeCl2 exists as a discrete molecule. (c) On the basis of the formal charges, which Lewis structure is expected to be dominant for BeCl2?