Question:
Nickel atom can lose two electrons to form Ni2+ ion. The atomic number of nickel is 28. From which orbital will nickel lose two electrons.
Solution:
One Ni atom has 28 electrons and its electronic configuration is : [Ar] 4s2 3d8
It becomes Ni2+ by losing 2 electrons, hence configuration of Ni2+ is : [Ar] 4s0 3d8
So, nickel loses two electrons from the 4s orbital, not the 3d orbital as per the Aufbau principle