The mass would be 28. The mass of an atom equals the number of neutrons and protons added together. In this case, they do not say the protons. But we must use our inside knowledge to know that the number of protons equals the number of electrons. Thus, your number of protons would be 13
The definition of a common ion as it applies to Le Chatelier's principle is an ion that is present in an equilibrium system and a compound added to the system. This is the case since in Le Chatelier's principle, it is based on an equilibrium system and where the reaction shifts to the left or to the right; towards the products or the reactants side.
The answer is B.
occur gradually over millions of years.
