Multiple Choice
In a water molecule (H_2O), what is the arrangement of all electron pairs (bonding and lone pairs) around the central oxygen atom?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Neutral Compounds
Multiple Choice
Which of the following best represents the Lewis dot structure for a neutral molecule of CO_2?
A
O–C–O, with each oxygen atom having three lone pairs
B
O=C=O, with each oxygen atom having two lone pairs
C
O≡C–O, with one oxygen atom having one lone pair and the other having three
D
O–C≡O, with the central carbon having two lone pairs
Verified step by step guidance1
Step 1: Determine the total number of valence electrons available for the CO_2 molecule. Carbon has 4 valence electrons, and each oxygen has 6 valence electrons, so total valence electrons = 4 + 2 × 6 = 16.
Step 2: Arrange the atoms with carbon as the central atom because it is less electronegative than oxygen. Connect the carbon atom to each oxygen atom with single bonds initially.
Step 3: Distribute the remaining valence electrons as lone pairs to satisfy the octet rule for the outer atoms (oxygen atoms first). Each oxygen should have 8 electrons around it (including bonding electrons).
Step 4: If the octet rule is not satisfied for the central carbon atom, form double bonds by converting lone pairs from oxygen atoms into bonding pairs between carbon and oxygen. This will help carbon achieve an octet.
Step 5: Verify the final Lewis structure by counting all electrons to ensure the total equals 16, and check that each atom (carbon and oxygens) has a complete octet. The correct structure will have carbon double bonded to each oxygen, and each oxygen will have two lone pairs.
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