Place the following in order of decreasing XO bond length, where "X" represents the central atom in each of the following compounds or ions.
1) CO₂, CO₃2⁻, SiO₃2⁻
2) CO₃2⁻, CO₂, SiO₃2⁻
3) CO₂, SiO₃2⁻, CO₃2⁻
4) CO₃2⁻, SiO₃2⁻, CO₂
5) SiO₃2⁻, CO₂, CO₃2⁻
6) SiO₃2⁻, CO₃2⁻, CO₂