examples of elements and compounds?
Visually inspect them to see if they are still good. If they look like they are wearing thin, replace them
If you have a shop manual it will tell you the minimum thickness,and then all you do is measure with a vermeer caliper. Or have a guy like me measure and tell you.
For an element, look at the periodic table. If the material has only the single element, such as a bar of gold (Au) silver (Ag) or copper (Cu) then it is an element material. But if it has a second element in the formula, then it is a compound. So gold chloride (AuCl) and silver chloride (AgCl) and cuprous chloride (CuCl) are compounds.
