The fluoride anion (F–) is formed when a fluorine atom gains an additional electron, resulting in a negative charge. To determine the correct Lewis dot structure, we begin by looking at the valence electrons of fluorine.
Fluorine has seven valence electrons (as it belongs to group 17 of the periodic table). When it gains one electron to become F–, the total number of valence electrons becomes eight. This configuration achieves a stable octet, which is the goal for most atoms.
In the Lewis dot structure for F–, we represent the seven original valence electrons as dots around the fluorine symbol (F). However, since it gained one more electron, we will visually indicate that by placing an additional dot, totaling eight dots.
The correct Lewis dot structure for the fluoride anion will have the symbol ‘F’ with eight dots arranged around it in pairs, reflecting the full octet:
. : F : .
In this structure, the paired dots represent the shared and lone pairs of electrons. The presence of the negative charge is often indicated, either through a superscript ‘-1’ near the ‘F’ or through wording accompanying the structure to reference the anion. Thus, we effectively represent the stable electron configuration of the fluoride anion.