Consider an element of air in the standard atmosphere at a standard altitude of 1000 m. Assume that you somehow raise this element of air isentropically to a standard altitude of 2000 m, where the element now takes on the standard pressure at 2000 m. Calculate the density of this isentropically raised element of air and compare it with the density of its neighboring elements of air that all have a density equal to the standard density at 2000 m. What does this say about the stability of the atmosphere in this case.