Multiple Choice
Which choice correctly identifies the oxidation number (o.n.) of sulfur in the compound Na2SO4?
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6. Chemical Quantities & Aqueous Reactions
Calculate Oxidation Numbers
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What is the bond order of the phosphorus-oxygen (P–O) bond in the phosphate ion, PO_4^{3-}?
A
1.33
B
2
C
1.25
D
1
Verified step by step guidance1
Write the Lewis structure of the phosphate ion, PO_4^{3-}. Phosphorus is the central atom bonded to four oxygen atoms, and the ion carries a -3 charge.
Count the total number of valence electrons: phosphorus has 5, each oxygen has 6, and add 3 extra electrons for the -3 charge. Calculate the total electrons available for bonding.
Distribute the electrons to form bonds and complete octets on the oxygen atoms. Typically, phosphorus forms one double bond with one oxygen and single bonds with the other three oxygens in resonance structures.
Recognize that the actual structure is a resonance hybrid of multiple Lewis structures where the double bond is delocalized over the four P–O bonds.
Calculate the bond order by dividing the total number of bonding electron pairs between phosphorus and oxygen by the number of P–O bonds. For phosphate, this is (1 double bond + 3 single bonds) / 4 = 1.25, or considering resonance, the bond order is approximately 1.33.
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