Sodium (Sodium) reacts with fluorine (Fluorine) to form Sodium Fluoride (Sodium Fluoride), whose chemical formula is $NaF $. The following describes this chemical knowledge in classical Chinese form:

Between heaven and earth, yin and yang sympathize, and all things change into life. Sodium is active, soft and silver-white in quality, dramatic in contact with water, turning qi and escape, and its nature is yang. Fluoride is the first of the halogen family, with light yellow-green gas, strong and poisonous in nature, and its nature is yin.

When sodium and fluorine meet, yin and yang are combined, and sodium loses one yang electron, fluoride gains it, and then forms sodium fluoride. The change of this combination is like the harmony of heaven and kun, and the harmony of rigidity and softness. Its sodium fluoride, stable, chemical formula is $NaF $, can be used in a variety of, or as a medical tooth fixing agent, or in industry to help.