Choose the appropriate word(s) from the bracket [+2, ethane, tetrahedral, square planar, zero, dry…

Choose the appropriate word(s) from the bracket [+2, ethane, tetrahedral, square planar, zero, dry cell, nickel-cadmium cell, propane, Wolff-Kishner, Stephen, completely filled, incompletely filled, paramagnetic, diamagnetic]: The complex compound $[\text{Ni}(\text{CO})_4]$ is ____ in shape and nickel is in ____ oxidation state in this complex compound.