Britannica Sources used in this answer

Why does periclase have a much higher melting point than halite?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Two diagrams show the three-dimensional structure of a methane molecule: panel A uses a ball-and-stick model with a central carbon atom connected to four hydrogen atoms in a tetrahedral arrangement, while panel B illustrates the bond angle of 109.5 degrees and bond length of 1.09 angstroms between carbon and hydrogen atoms. — chemical compound Methane, in which four hydrogen atoms are bound to a single carbon atom, is an example of a basic chemical compound. The structures of chemical compounds are influenced by complex factors, such as bond angles and bond length.

Periclase (MgO) has a significantly higher melting point than halite (NaCl) primarily due to the strength of the electrostatic forces holding the crystal lattice together.

In chemistry, the strength of the ionic bond is determined by the charges of the ions and the distance between them. Halite consists of sodium ( $N a^{+}$ ) and chlorine ( $C l^{-}$ ) ions, which carry a charge of $\pm 1$ . In contrast, periclase is composed of magnesium ( $M g^{2 +}$ ) and oxygen ( $O^{2 -}$ ) ions, which carry a charge of $\pm 2$ . Because the electrostatic attraction between ions is directly proportional to the product of their charges, the bonds in periclase are much stronger than those in halite.1

While both minerals share the same isometric crystal structure, the higher charge density of the magnesium and oxygen ions in periclase requires significantly more thermal energy to overcome the lattice energy and transition the substance from a solid to a liquid state.1