How many $\text{EDTA}$ (ethylenediaminetetraacetic acid) molecules are required to make an octahedral complex with a ${\text{Ca}}^{2+}$ ion?

${\text{EDTA}}^{4-}$ is a hexadentate ligand. It has six donor atoms ($2$ Nitrogen and $4$ Oxygen atoms) that can simultaneously bind to a single metal ion, occupying all six positions in an octahedral coordination sphere.