Question

Which of the following cannot be regarded as molecular solid?
(a)SiC
(b)AlN
(c)Diamond
(d)All of the above

Answer 1

One of the four fundamental states of matter is solid (the others being liquid, gas and plasma). A solid's molecules are tightly packed and contain the least amount of kinetic energy. A solid's structural rigidity and resistance to a force applied to its surface are its distinguishing characteristics. A solid item, unlike a liquid, does not flow to take on the shape of its container or expand to cover the full available volume, as a gas does.

Complete answer:
The term "molecular solid" refers to a solid made up of distinct molecules. Van der Waals forces, dipole-dipole interactions, quadrupole interactions, - interactions, hydrogen bonding, halogen bonding, London dispersion forces, and in some molecular solids, coulombic interactions are the cohesive forces that hold the molecules together. Unlike metallic and some covalent bonds, intermolecular interactions seldom include delocalized electrons.
A network solid, also known as an atomic crystalline solid, is a chemical compound (or element) in which the atoms are held together by covalent bonds in a continuous network that runs the length of the substance. There are no individual molecules in a network solid, therefore the entire crystal or amorphous solid can be called a macromolecule. Like ionic compounds, network solids formulas are simple ratios of the component atoms represented by a formula unit.
Diamond, which has a continuous network of carbon atoms and silicon dioxide, and quartz, which has a continuous three-dimensional network of $Si{{O}_{2}}$ units, are examples of network solids. Graphite and the mica group of silicate minerals are made up of layers of continuous two-dimensional sheets that are covalently linked inside the layer and held together by other bond types. Glasses are solids with a disordered network structure. These are generally produced when melts are rapidly cooled, leaving little time for atomic ordering to take place.
Hence option d is correct.

Note:
A solid's atoms are held together either in a regular geometric lattice (crystalline solids, such as metals and typical ice) or in an irregular lattice (an amorphous solid such as common window glass). Solids cannot be squeezed at low pressures, but gases can be compressed at low pressures due to the loose packing of the molecules in a gas.