The sulfate ion, SO₄²⁻, can be represented by Lewis structures that differ in the number of S–O double bonds.
A. All four S–O bonds are single bonds.
B. One S–O bond is a double bond and the other three are single bonds.
C. Two S–O bonds are double bonds and the other two are single bonds.
D. All four S–O bonds are double bonds.
Based solely on formal-charge considerations and acceptable valence-shell electron counts, which structure is the most plausible?
a) A
b) D
c) C
d) B