How do the electron configurations within a group compare

Explanation:

This table shows how the electron configurations of the representative groups can be compared.

Group        last shell of the electron configuration

1                 n s¹

2                n s²

13               n s² p¹

14               n s² p²

15               n s² p³

16               n s² p⁴

17               n s² p⁵

18               n s² p⁶

That means that, for example, that the electron configurations of all the elements of the group 17, halogens (F, Cl, Br, I, At, Ts) terminate is n s² p⁵, where n is the principal quantum number (main energy level), which may take the numbers 1, 2, 3, 4, 5, 6, or 7.

And this structure shows the reason behind the similarity of the chemical properties of the elements within a group, given that the outermost electrons, i.e the valence electrons, are which mostly participate in the chemical reactions.

For the gropus 3 trhough 12, the metal transitions, the comparison must include the filling of the orbitals d and f.

the answer is c. nacl