Confusion in R/S Nomenclature and Chirality [closed]

I have many confusions regarding optical isomerism:

What is the use of the R/S nomenclature? I understand that it is used to distinguish between the different spacial arrangements that are possible for a molecule, but i have few questions.

• I believe R/S nomenclature can only be used for a chiral center. Now, say we have a two chiral center molecule, so there are 4 types of different molecules (because 4 different configurations are possible) are possible, according to me, (R,R), (R,S),(S,S),(S,R). Am i right? Are all these 4 molecules different?

• I am getting confused when we introduce chirality here. If the molecule is achiral then will some of the above four become the same molecule? If the compound is chiral, will all the above 4 be different from each other?

• Generalizing, if a molecule has n chiral center, will it always have $$2^{n}$$ different isomers, irrespective of whether it is chiral or not, or am I wrong in thinking so? Please correct me

You are right that the presence of two chiral centres ($$n = 2$$) may yield four permutations, namely (R,R), (R,S), (S,R), or (S,S). However, depending on the overall structure of the molecule in question, $$2^n$$ is the maximum number of different molecules.