Which two elements on the periodic table have the same number of electron shells?

Potassium (K #19) and Strontium (Sr #38)

Radon (Rn #86) and Cesium (Cs #55)

Fluorine (F #9) and Sodium (Na #11)

Sulfur (S #16) and Oxygen (O #8)

Fluorine (F #9) and Sodium (Na #11)