Can anyone answer this A levels chemistry question? The answer A, I just need the explanation.

1) how many electrons are in each energy level of the following elements? a. he b. na c. na d. ne 2) how many valence electrons are percent in the following atoms? a. s b. mg c. be d. cl 3) which of the following elements are stable as atoms? a. he b. o c. cl d. ar if you are able to provide the work as to how you got the answers that would be greatly appreciated. : )

Which atom or ion is the largest? a. k b. k+ c. ca d. ca2+ e. li

‘which reaction would most likely require the use of an inert electrode?