Why is the Electron Configuration for Ti+2 [Ar]3d2?

[τheory]

Homework Statement

What is the electron configuration for Ti⁺²? The answer to this question, from my homework, is [Ar]3d², but I am not able to figure out why.

2. The attempt at a solution
I originally thought the configuration was:
Ti⁺² = [Ar]4s²

and not:
Ti⁺² = [Ar]3d²

My reasoning was that if titanium itself, neutrally, is [Ar]4s²3d², then wouldn't, in this cation, taking away 2 electrons be more stable from the 3d sub-shell rather than the 4s sub-shell?

Taking from the 4s sub-shell would leave 2 unpaired electrons in the 3d sub-shell, while taking from the 3d subshell would leave a complete electron pair in the 4s sub-shell, meaning more stability? Or is this thinking invalid?

 

[Infinitum]

Homework Statement

What is the electron configuration for Ti⁺²? The answer to this question, from my homework, is [Ar]3d², but I am not able to figure out why.

2. The attempt at a solution
I originally thought the configuration was:
Ti⁺² = [Ar]4s²

and not:
Ti⁺² = [Ar]3d²

My reasoning was that if titanium itself, neutrally, is [Ar]4s²3d², then wouldn't, in this cation, taking away 2 electrons be more stable from the 3d sub-shell rather than the 4s sub-shell?

Taking from the 4s sub-shell would leave 2 unpaired electrons in the 3d sub-shell, while taking from the 3d subshell would leave a complete electron pair in the 4s sub-shell, meaning more stability? Or is this thinking invalid?

Even though 3d comes after 4s in order of filling the sub-shells, 4s has the higher energy level since n=4, and electron almost always comes out from the outermost energy shell.