Lithium fluoride (LiF) is an ionic compound. Its Lewis structure consists of a positively charged lithium ion (Li?) and a negatively charged fluoride ion (F?). The lithium ion (Li?) and the fluoride ion (F?) are enclosed in brackets, and they are connected by an ionic bond. The specific structure is shown in the diagram below:

According to the periodic table, lithium metal has one valence electron in its outermost shell and is highly electropositive. It has a low ionization enthalpy, making it easy to lose an electron even with a small input of energy. A fluorine atom has seven valence electrons in its outermost shell and is highly electronegative; it readily gains an electron to achieve a stable octet configuration. Consequently, lithium metal transfers its single valence electron to the fluorine atom, becoming a lithium ion [Li?]. The fluorine atom gains an electron to become a fluoride ion [F?], and the two ions are held together by an ionic bond.