First we have to identify the charge of the cobalt ion in the tetrahedral complex `[CoCl_4]^(2-)` .
`x + (-1 x4) = -2`
`x = -2 + 4`
`x = +2 = Co^(2+)`
Looking at the periodic table we can see that the element cobalt has a configuration of `4s^2 3d^7` and the cobalt ion would be `3d^7` .
For tetrahedral complexes the crystal field splitting diagram will have its t2g orbitals higher than the eg orbitals.
__ __ __ `t_(2g)`
__ __ `e_g`
Filling up the diagram would lead us having two paired orbitals (2 `e_g` 's) and three unpaired electrons on the `t_(2g)` orbitals.