Question

.a sodium atom has the following distribution of electrons in its energy cells:
shell1: 2 electrons
shell2: 8 electrons
shell3: 1 electron

I think its shell 2

Answer 1

Your answer makes no sense. The atom contains all three shells. Na is element #11.

I think you omitted the question you are answering using the given data. (And I suspect it is shell 3)