The correct answer is Ga3+.
Electron configuration of Al is [Ne] 3s2 3p1
Electron configuration of Al3+ is [Ne]
So the electron configuration of Al3+ is like that of Ne.
Electron configuration of Sc is [Ar] 3d1 4s2
Electron configuration of Sc3+ is [Ar]
So the electron configuration of Sc3+ is like that of Ar.
Electron configuration of As is [Ar] 3d10 4s2 4p3
Electron configuration of As3- is [Ar] 3d10 4s2 4p6
So the electron configuration of As3- is like that of Kr
Electron configuration of Kr [Ar] 3d10 4s2 4p6
Electron configuration of Ga is [Ar] 3d10 4s2 4p1
Electron configuration of Ga3+ is [Ar]3d10
The presence of the ten d orbital electrons prevents Ga3+ from having the same electron configuration as Argon.
All other choices have the same electron configurations as a noble gas.
