Thallium(I) fluoride
Thallium fluoride is the inorganic compound with the formula TlF. It is a white solid, forming orthorhombic crystals. The solid is slightly deliquescent. It has a distorted sodium chloride crystal structure, due to the 6s2 inert pair on Tl+.
This salt is unusual among the thallium(I) halides in that it is very soluble in water.