What is the formula of the ionic compound expected to form between the elements f and ca?

Ionic compounds are compounds made up of elements in which one has the tendency to loose electrons whereas the other has the tendency to gain electrons. Loss of electron results in the formation of a positively charged ion (cation) while gain of electrons results in the formation of negatively charged ions (anions). Usually metals have the tendency to loose electrons and non-metals tend to gain electrons.

Calcium (Ca) is a metal and belongs to group IIA in the periodic table with a valence electron configuration of 4s2

Fluorine (F) is a non-metal and belongs to group VIIA in the periodic table with a valence configuration of 2s22p5.

Thus, Ca will donate its outer 2 electrons to F, thus allowing each of the electronegative F atoms to complete its octet.

Therefore, we have:

Ca2+   +    F-           CaF2

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements