From the following elements, which has a completely filled outer shell?

The element that has a completely filled outer shell is Neon. Neon is part of the noble gases group and has an atomic number of 10. Its electron configuration is 1s² 2s² 2p⁶, which means that its outermost shell (the second shell, in this case) contains a total of eight electrons (two in the 2s subshell and six in the 2p subshell). This full outer shell configuration is what makes Neon chemically stable and nonreactive, which is characteristic of noble gases.

In contrast, Oxygen, Fluorine, and Nitrogen do not have completely filled outer shells. Oxygen, with an atomic number of 8, has six electrons in its outer shell and needs two more to achieve a full octet. Fluorine, with an atomic number of 9, has seven electrons in its outer shell and requires one more for stability. Nitrogen, with an atomic number of 7, has five outer electrons and needs three more to fill its outer shell. Therefore, only Neon possesses a fully filled outer shell among the options provided.