The term COMMON FLUORINE PARTNER is solved by the 3-letter word TIN. TIN is a chemical element with the symbol Sn and atomic number 50. It is a silvery-white metal that is malleable and ductile. TIN is often found in combination with other elements, such as fluorine, and is commonly used in alloys, such as bronze and pewter. TIN is also used in many industrial applications, including soldering and TIN plating.