Final answer:
The correct electron configuration for Zirconium (Zr) is [Kr] 4d² 5s², which demonstrates the filling of the 5s orbital and then the 4d orbital following the principal quantum number order.
Step-by-step explanation:
The electron configuration for Zirconium (Zr) can be determined by following the order of orbitals based on their energy levels. Starting from the nearest noble gas which is Krypton (Kr) as a core, we continue with the 4d and 5s orbitals, which are of higher energy than those represented in the Krypton core. The electronic configuration of Zirconium should thus show the occupation of these orbitals. The correct electron configuration for Zirconium (Zr) is [Kr] 4d² 5s².
Recall that transition metals fill their d orbitals after filling the s orbitals of the same principal quantum number. Hence, Zirconium, with atomic number 40, would fill the 5s orbital before starting to fill the 4d orbital. Zirconium has two electrons in the 5s orbital and continues to fill the 4d orbital with its remaining four electrons, which results in 4d². It is important to remember that the previously mentioned configuration [Kr] 4d² 5s² represents a neutral Zirconium atom.