Multiple Choice
Which of the following statements correctly describes the Lewis structure and resonance of HCN (hydrogen cyanide)?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Exceptions
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In the Lewis dot structure of PF_3, how many lone pairs of electrons are present on the phosphorus (P) atom?
A
1
B
2
C
0
D
3
Verified step by step guidance1
Determine the total number of valence electrons for the phosphorus (P) atom. Phosphorus is in group 15 of the periodic table, so it has 5 valence electrons.
Recognize that in PF_3, phosphorus forms three single bonds with three fluorine atoms. Each bond uses 2 electrons, but only 1 electron from phosphorus is counted per bond.
Calculate the number of electrons phosphorus uses in bonding: since there are 3 bonds, phosphorus uses 3 of its valence electrons for bonding.
Subtract the bonding electrons from the total valence electrons of phosphorus to find the remaining electrons, which will be lone pairs on phosphorus.
Divide the remaining electrons by 2 to find the number of lone pairs on phosphorus, since each lone pair consists of 2 electrons.
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