The molecule PF3, which stands for phosphorus trifluoride, forms a covalent bond. In a covalent bond, atoms share electrons to achieve a stable electron configuration. Phosphorus (P) and fluorine (F) are both nonmetals, and when they combine, they share electrons rather than transferring them completely.
In the case of PF3, phosphorus has five valence electrons (electron configuration: 3s^2 3p^3) and requires three more electrons to complete its octet. Each fluorine atom has seven valence electrons (electron configuration: 2s^2 2p^5) and requires one more electron to complete its octet.
Phosphorus shares its three valence electrons with three fluorine atoms, forming three covalent bonds. The resulting molecule, PF3, has a trigonal pyramidal shape, with phosphorus in the center and three fluorine atoms bonded to it.
Ionic bonds typically form between metals and nonmetals, where there is a complete transfer of electrons from one atom to another. Since both phosphorus and fluorine are nonmetals and they share electrons in PF3, it is classified as a covalent bond.