Multiple Choice
Which of the following statements correctly describes the Lewis dot structure of the KrF_2 molecule?
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11. Bonding & Molecular Structure
Lewis Dot Structures: Ions
Multiple Choice
Which of the following statements correctly describes the Lewis dot structure of the PF_4^- ion?
A
Phosphorus is surrounded by four fluorine atoms, with each fluorine having three lone pairs, and the extra negative charge is placed as a lone pair on phosphorus.
B
Phosphorus is surrounded by four fluorine atoms, each with three lone pairs, and the extra negative charge is distributed as an additional lone pair on one of the fluorine atoms.
C
Phosphorus is surrounded by four fluorine atoms and has one lone pair, resulting in a total of 10 electrons around phosphorus.
D
Phosphorus is surrounded by four fluorine atoms, each with three lone pairs, and the extra negative charge is distributed over the entire ion, resulting in a total of 36 valence electrons.
Verified step by step guidance1
Determine the total number of valence electrons for the PF_4^- ion by adding the valence electrons from phosphorus, fluorine atoms, and the extra electron due to the negative charge. Phosphorus has 5 valence electrons, each fluorine has 7, and the negative charge adds 1 more electron. So, total electrons = 5 + (4 \(\times\) 7) + 1.
Draw the skeletal structure with phosphorus as the central atom bonded to four fluorine atoms. Each P-F bond represents 2 electrons.
Assign lone pairs to each fluorine atom to complete their octets. Since each fluorine needs 8 electrons total and shares 2 in the bond, each fluorine will have 6 electrons as lone pairs (3 lone pairs per fluorine).
Check the remaining electrons after bonding and lone pairs on fluorine. These leftover electrons will be placed as lone pairs on the phosphorus atom or distributed as the extra negative charge.
Verify the total electron count around phosphorus and fluorine atoms, ensuring the octet rule is satisfied for fluorine and considering the expanded octet possibility for phosphorus. The extra negative charge is generally delocalized over the ion, not localized solely on phosphorus or a single fluorine.
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