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Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids. [64]
This often causes ionic compounds to be very stable. Ionic bonds have high bond energy. Bond energy is the mean amount of energy required to break the bond in the gaseous state. Most ionic compounds exist in the form of a crystal structure, in which the ions occupy the corners of the crystal.
Low-temperature ionic liquids can be compared to ionic solutions, liquids that contain both ions and neutral molecules, and in particular to the so-called deep eutectic solvents, mixtures of ionic and non-ionic solid substances which have much lower melting points than the pure compounds. Certain mixtures of nitrate salts can have melting ...
Melting points are typically moderately high, but some combinations of molecular cations and anions yield an ionic liquid with a freezing point below room temperature. Vapour pressures in all instances are extraordinarily low; this is a consequence of the large energy required to move a bare charge (or charge pair) from an ionic medium into ...
For ionic compounds made of molecular cations and/or anions, there may also be ion-dipole and dipole-dipole interactions if either molecule has a molecular dipole moment. The theoretical treatments described below are focused on compounds made of atomic cations and anions, and neglect contributions to the internal energy of the lattice from ...
Metal cations with a high oxidation state tend to undergo hydrolysis instead, e.g. ferric chloride, aluminium chloride, and titanium tetrachloride. [1] Discrete metal halides have lower melting and boiling points. For example, titanium tetrachloride melts at −25 °C and boils at 135 °C, making it a liquid at room temperature.
Many cage-like compounds like adamantane and cubane with high symmetry have relatively high melting points. A high melting point results from a high heat of fusion, a low entropy of fusion, or a combination of both. In highly symmetrical molecules the crystal phase is densely packed with many efficient intermolecular interactions resulting in a ...
In compounds, sodium is usually ionically bonded to water and anions and is viewed as a hard Lewis acid. [25] Two equivalent images of the chemical structure of sodium stearate, a typical soap. Most soaps are sodium salts of fatty acids. Sodium soaps have a higher melting temperature (and seem "harder") than potassium soaps. [24]