What is the correct formula for lithium fluoride?
A. $ LiF $
B. $ L{i_2}{F_2} $
C. $ L{i_3}F{F_9} $
D. $ Li{F_7} $
E. $ L{i_7}{F_{19}} $

Hint :Lithium fluoride is an inorganic compound and it is a colourless solid and the molecular weight of lithium fluoride is $ 26 $ g/mol. Lithium fluoride is an inorganic compound and the chemical formula is $ LiF $ . It does not have any colour or it is colourless solid that converts to white colour with gradually decreasing crystal size.

Complete Step By Step Answer:
Although odourless, lithium fluoride has a quite bitter and saline taste. Its shape and structure is similar to that of sodium chloride, but it is not much mixable with water. It is mainly used as a component of molten salts.
It is prepared from lithium hydroxide or lithium carbonate along with hydrogen fluoride. It can also be created by reacting sulphur hexafluoride with metallic lithium, as in the engine of Mark 50 torpedo, but the pathway is industrially not used because of the high cost of reagents.
Huge, pure crystals of lithium fluoride are deployed in optical systems for ultraviolet, visible, or infrared light and also in X-ray.
It is used in brazing or soldering fluxes and also in welding the rod coatings.
It is also an important source of creating fluoride glasses in infrared optical applications.
 $ LiF $ is the correct formula for lithium fluoride. $ Li $ has a positive charge $ + 1 $ and $ F $ has negative charge $ - 1 $ so, when they mix with each other, so that to form $ LiF $ which have ionic bonds.
Hence, Option A is correct.

Note :
Don’t get confused by the options as only one is correct and by name it just contains $ + 1 $ and $ - 1 $ charge of $ Li $ and $ F $ respectively.pure crystals of lithium fluoride are deployed in optical systems for ultraviolet, visible, or infrared light and also in X-ray.