Some substances like chalk, duster, paper, wood, air are not found in the periodic table. why?

They are not pure elements, instead they are compounds, hence why they are not found on the periodic table. (Periodic table only consists of pure elements)

there are no statements provided but here is why:

sulfur belongs to group 16 because it can be found in nature whether it is in a free or combined state.

hope this

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