15. Why does the mass on the periodic table for a particular element not equal the mass of any atom of
that element.

Mass number is always an integer. Atomic mass is never an integer number for several reasons: The atomic mass reported on a periodic table is the weighted average of all the naturally occuring isotopes. ... The mass of an atom isn't what you'd get by adding up the masses of its individual protons, neutrons and electrons.

Explanation:

he uptake of drugs from the intestine is often strongly influenced by diffusion. for example, consider a water-insoluble steroid for treating inflammation that is solubilized in aggregates of detergent molecules, called micelles. these micelles, aggregates of 80 soap molecules, have a molecular weight of 24,000, a diameter of 2.6 nm, and a charge of -27. the positively charge ions (counterions) in this system are na".