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.
The reason for this is similar to the reason that covalent compounds have low melting and boiling points. When you hit an ionic compound with something, it feels very hard. The reason for this is that all of the ionic bonds which hold together the crystal tend to make it very inflexible and hard to move.here are a couple of exceptions to this rule. The first is with covalent compounds that contain neither carbon nor hydrogen. These tend not to burn, and if they do, they burn by mechanisms other than the classic combustion reaction. The other exception comes with ionic compounds referred to as organic salts.