Final answer:
An element with the electronic configuration [36 Kr], 5s² is located in period 5 of the periodic table, as the highest principal energy level filled is the 5th.
Step-by-step explanation:
The element with the electronic configuration [36 Kr], 5s² indicates that the last electrons are being added to the 5s subshell. Since the highest principal energy level filled in an element's electron configuration corresponds to its period number on the periodic table, we can deduce that this element is in period 5. The noble gas preceding the configuration is krypton, which has an atomic number of 36; hence the electron configuration following [Kr] continues with 5s², placing the element in period 5.