monofluorides

Monofluorides are chemical compounds that contain exactly one fluoride ion per formula unit, typically written as MF. The term is most often applied to ionic salts and simple fluorides in which a metal or other cation is counterbalanced by a single fluoride anion. They are contrasted with difluorides (MF2) and higher polyfluorides.

In their solid state, monofluorides are predominantly ionic, with F− forming a lattice together with the cation M. The bonding is generally strong electrostatic, leading to high lattice energies. In some cases, especially with copper or silver, a degree of covalent character can appear in the metal–fluorine bonds, giving partial covalency to the compound.

Common examples include alkali metal fluorides such as sodium fluoride (NaF) and potassium fluoride (KF), as well as copper(I) fluoride (CuF) and silver fluoride (AgF). Solubility and stability vary widely: alkali fluorides are typically soluble in water, whereas many transition‑metal monofluorides are less soluble and can be prone to hydrolysis or disproportionation under some conditions.

Methods of preparation include direct fluorination of a metal with fluorine gas (M + F2 → MF) and metathesis routes that use fluoride sources to precipitate the desired MF from metal salts. Monofluorides also arise as intermediates in the synthesis of more complex fluorides.

Uses of monofluorides are varied. They serve as laboratory reagents and starting materials for further fluorination chemistry. NaF, in particular, is widely used in toothpaste and water fluoridation, while other MF compounds find utility as catalysts, fluxes, or precursors in materials chemistry.

Safety: many fluoride compounds can be toxic, and hydrogen fluoride is especially hazardous. Appropriate handling and protective equipment are essential when working with monofluorides.