Complex sleep apnea is the term used to describe a form of sleep disordered breathing in which repeated central apneas (>5/hour) persist or emerge when obstructive events are extinguished with positive airway pressure (PAP) and for which there is not a clear cause for the central apneas such as narcotics or systolic heart failure.
Giant covalent structures. Such as silicon dioxide, have extremely high melting points and low solubility in all solvents. They are non-volatile and conductivity depends on the availability of electrons in the valence shell (eg graphite). If all electrons are used in bonding they are insulators.ow melting points:- The bonds between molecules are very weak, especially when the molecules are small. It only requires a small quantity of heat energy to create enough molecular vibration to break the molecules attraction for one another and the solid melts.
It's these weak intermolecular forces that determine many of the properties of covalent molecular compounds. Elemental Composition of Covalent Compounds. Compounds that contain both metals and nonmetals are usually ionic, not covalent. So KBr and Na. Properties of Covalent Molecular Compounds. 1  Low melting points and boiling points. 2  Low enthalpies of fusion and vaporization These properties are usually one or two orders of magnitude smaller than they are for ionic compounds. 3  Soft or brittle solid forms. 4  Poor electrical and thermal conductivity.