Question

The filling of which orbital is represented by the transition metals in period 4?

Answer 1

The 4s orbital has a lower energy than the 3d, and so fills next. That fits with the chemistry of potassium and calcium and the entire period. So the answer is 3d

Answer 2

Answer: 3d

Explantion:

1) Period 4 contains the elements with atomic numbers 19 through 36.

2) The elements with atomic numbers 19 (K) and 20 (Ca) fill the orbital 4s.

3) After that, as Aufbau's rule may help you to remember, the energy of the orbitals 3d is lower than the energy of the orbtitals 4p. So, the element 21 (Sc) start fillind the orbital 3d.

There are ten 3d orbitals, so the elements 21 through 30 fill the 3d orbitals.

Those elements, called transition metals are: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

When the 3d orbitals are full, the next elements in the same period 4, fill the six 4p orbitals.