Final answer:
The chromium ion is the element commonly found in chromates, oxalates, and dichromates in different oxyanion forms, such as CrO₄²⁻ in chromates and Cr₂O₇²⁻ in dichromates.
Step-by-step explanation:
The ion commonly found in chromates, oxalates, and dichromates is the chromium ion. However, the charge and form this ion takes in each compound are different.
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- Chromates contain the chromate ion, CrO₄²⁻.
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- Oxalates contain the oxalate ion, C₂O₄²⁻, but chromium can be present in the form of a chromium(III) complex, as in Cr(C₂O4)₃³⁻.
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- Dichromates contain the dichromate ion, Cr₂O₇²⁻.
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Therefore, although the exact ion form for chromium differs, the common element is chromium associated with different oxyanions.