while elements and compounds can both be classified as pure substances because they have distinct properties and composition, cannot be decomposed further.

elements

Explanation:-

Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions. Example: Cobalt

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water

Thus element is the pure substance that cannot be decomposed further.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.