1. Electronic Configuration:

* Krypton's atomic number is 36, meaning it has 36 electrons.

* Its electronic configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶

2. Identifying the Third Energy Level:

* The third energy level is denoted by the principal quantum number (n) = 3.

* This means we're looking at the electrons in the 3s, 3p, and 3d sublevels.

3. Filled Sublevels:

* 3s²: The 3s sublevel is filled with 2 electrons.

* 3p⁶: The 3p sublevel is filled with 6 electrons.

* 3d¹⁰: The 3d sublevel is filled with 10 electrons.

Therefore, the sublevels of the third energy level that are filled in krypton are 3s, 3p, and 3d.