Which 2+ ion has two 3d electrons? which has eight 3d electrons?

1) Titanium cation has two 3d electrons.
₂₂Ti 1s²2s²2p⁶3s²3p⁶3d²4s².
₂₂Ti²⁺1s²2s²2p⁶3s²3p⁶3d²4s⁰.
2) Nickel cations has eight 3d electrons.
₂₈Ni 1s²2s²2p⁶3s²3p⁶3d⁸4s².
₂₈Ni²⁺ 1s²2s²2p⁶3s²3p⁶3d⁸4s⁰.
Both cations (titanium and zinc) lost two electrons from 4s orbital, because 4s orbital is far away from nucleus.

Because it was a dramatically big guy