How does a cap rock allow humans to access oil and natural gas reserve?

Cap rocks form the top of reservoirs and create a layer that is impervious to fluid flow By preventing fluids from flowing through it, the fluids are prevented from escaping the reservoir. This applies to oil and gas reservoirs. Oil and gas reservoirs often form in "traps"

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.