Think about the gas released as a result of fracking shale. compare this energy resource to the conventional resources we have been using throughout the last one-hundred and fifty years. using the model seen here, compare the age of the coal we have been using to the gas produced by the fracked marcellus shale. a) coal formations are much younger than the shale. b) coal and shale formations are about the same age. c) the shale is younger than the coal formations we use today. d) scientists cannot determine which layer is older than the other.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.