Multiple Choice
After drawing the Lewis structure of AsF_5, what is the ideal F–As–F bond angle around the central arsenic atom?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Exceptions
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Which of the following molecules cannot be represented by a conventional Lewis dot structure due to its electron deficiency?
A
CO2
B
NH3
C
BF3
D
H2O
Verified step by step guidance1
Understand that a conventional Lewis dot structure represents molecules by showing all valence electrons as bonding or lone pairs, aiming to satisfy the octet rule for each atom (except for some exceptions).
Identify that electron deficiency occurs when a molecule has a central atom with fewer than eight electrons around it after drawing all bonds and lone pairs, making it impossible to complete the octet using only conventional Lewis structures.
Examine each molecule: CO2, NH3, H2O, and BF3, by counting the valence electrons and attempting to complete the octet for the central atom.
Recognize that CO2, NH3, and H2O can all be drawn with complete octets on their central atoms using conventional Lewis structures, while BF3 has only six electrons around boron, making it electron deficient.
Conclude that BF3 cannot be represented by a conventional Lewis dot structure that satisfies the octet rule for boron, which is why it is electron deficient.
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