Question

What is the first element to start filling a d sublevel?

Answer 1

Scandium  is  the  first   element  to  fill  the   d   sublevel.The  d  orbital  are  occupied  transition metals  and  Scandium  is a  transition  metal  with  atomic  number 21  thus  has  the  following  electron  configuration  (Ar) 3d^1  4s^2.   From  this  electronic   configuration scandium  has  only  one  electron  in  the  d  subshell.

Answer 2

The answer would be Scandium, with an atomic number of 21. This is a chemical element with symbol Sc and atomic number 21. A silvery-white metal d-block element, it has archaeologically been ordered as a rare earth element, organized with yttrium and the lanthanides.