Why are there many butt limited combinations of elements that make compounds

We have limited combinations of elements to make compounds because most of the compounds are not stable due to different chemical properties of elements.

Elements combine to form compounds but not all of the elements combine in the same way. The individual properties of each element must be taken into account before combining them.

The most common types of compounds are metallic compounds, ionic compounds, and covalent compounds. All compounds made in the laboratory are not stable and the same phenomenon occurs in nature as well. Elements that have more tendency to react with other elements are far less than the total number of elements in the periodic table.

Every element tries to make a bond with another element that fulfill the requirements of both of them. For example if an element needs to lose its one electron will always try to make compound with another element that will have the tendency to gain one electron. They will not make bond with other random element so in this way  the combinations of elements that make compounds becomes limited.

snell's law

refractve index = sin incidence / sin refraction