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Examples of network solids include diamond with a continuous network of carbon atoms and silicon dioxide or quartz with a continuous three-dimensional network of SiO 2 units. Graphite and the mica group of silicate minerals structurally consist of continuous two-dimensional sheets covalently bonded within the layer, with other bond types ...
A network covalent solid consists of atoms held together by a network of covalent bonds (pairs of electrons shared between atoms of similar electronegativity), and hence can be regarded as a single, large molecule. The classic example is diamond; other examples include silicon, [3] quartz and graphite.
In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal. [1] [2] It can also refer to the chemical formula for that unit. Those structures do not consist of discrete molecules, and so for them, the term formula unit is used.
Typically, a molecular solid is ductile when it has isotropic intermolecular interactions. This allows for dislocation between layers of the crystal much like metals. [5] [8] [11] For example, plastic crystals are soft, resemble waxes and are easily deformed. One example of a ductile molecular solid, that can be bent 180°, is hexachlorobenzene ...
Such covalent substances are usually gases, for example, HCl, SO 2, CO 2, and CH 4. In molecular structures, there are weak forces of attraction. Such covalent substances are low-boiling-temperature liquids (such as ethanol), and low-melting-temperature solids (such as iodine and solid CO 2).
[412] [n 43] In organic chemistry, carbon can form complex cations – termed carbocations – in which the positive charge is on the carbon atom; examples are CH + 3 and CH + 5, and their derivatives. [413] Graphite is an established solid lubricant and behaves as a semiconductor in a direction perpendicular to its planes. [407]
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Gels consist of a solid three-dimensional network that spans the volume of a liquid medium and ensnares it through surface tension effects. This internal network structure may result from physical bonds such as polymer chain entanglements (see polymers) (physical gels) or chemical bonds such as disulfide bonds (see thiomers) (chemical gels), as well as crystallites or other junctions that ...