Element with the electronic configuration as [Ar]18 3d5 4s1 is placed in?
Let's look at the electronic configuration of the given element [Ar]18 3d5 4s1.
As we studied in the last chapter we can see that instead of filling 4s fully, the d orbital is half-filled.
Try to recall the concept of fully filled and half-filled orbitals.
Do you remember that fully filled and half-filled orbitals are more stable?
Fully filled and half-filled orbitals are more stable because of symmetric distribution and exchange energy.
Now you can see that the same thing happening in this configuration.Therefore, we can say that this is a d-block element and because its atomic number is 24, it will be placed in VIB group.