Answer:
My apologies for the rotated picture. The work is nonetheless correct.
Step-by-step explanation:
Na (Sodium) is an alkali metal, and its valence shell contains 1 electron when it is an atom (not an ion). Elements with one, two, and three valence electrons "prefer" to lose an electron so that their valence shell "feels" stable. F (Fluorine) is a nonmetal and a halogen. Halogens have 7 valence electrons, and would "prefer" to gain an electron in order to "feel" stable. With 8 valence electrons, a halogen essentially acts like a noble gas (which have 8 valance electrons as atoms), which is beneficial because it will almost always increase the stability of the molecule, which is what atoms seek when they form bonds. Now, if an electron is negatively charged, and an element gains an electron, they have gained a negative. Thus, an atom that gains an electron will become an anion, a negatively charged ion. The opposite is true when elements lose an electron. In this case, an atom becomes a cation, a positively charged ion. Therefore, Na loses an electron and becomes a cation, while F gains an electron and becomes an anion.