PART 4: d-block elements (first row)
The first row transition elements:
electron configurations are [Ar]…
4s23d1
4s23d2
4s23d3
4s13d5
4s23d5
4s23d6
4s23d7
4s23d8
4s13d10
4s23d10
Note: for Cr and Cu it is more energetically favorable to half-fill or completely fill the d sub-level so they have only one 4s electron