How many electrons can the n=4 shell hold?
a. 8
b.16
c.32
d.64

             32 Electrons

                    In statement the letter "n" specifies the Principle Quantum Number. Principle Quantum number is main energy level of an atom. Hence, n = 4 means we are talking about the fourth energy level or fourth shell of an atom.

                    Also, the number of electrons present in any main energy level are calculated by using following formula,

                                                         2n²

Hence, as,

                 n = 4

So, by putting this value in above formula,

                                                         2 (4)²

                                                         2 (16)

                                                         32