What is the ratio of calcium to fluorine atoms when calcium fluoride makes a crystal

Calcium is a Group 2 metal. Fluorine is a Group 17 gas. Towards the right of the Periodic table, ELEMENTS tend to get smaller as the increased nuclear charge exerts a greater attractive force on the valence electrons. The small fluorine atom tends to attract electrons, and is energetically most stable when it forms the  F −  ion.  On the other hand, calcium is a large Group 2 metal. It has 2 valence electrons, which are in the valence (the outermost) shell, and nuclear charge is somewhat diminished for these electrons. Calcium tends to be oxidized (to lose electrons) to form  C  a  2 +  ions.  So if calcium and fluorine want to make music together (or at least form a chemical bond), then a formula of  (C  a  F  2)  is entirely reasonable (why? because this combination is electrically neutral!). And in fact in nature the mineral fluorite ( C  a F 2 ) is very widespread.