Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances: (a) \(\mathrm{CaCl}_{2}\) (b) SiC (c) \(\mathrm{N}_{2}\) (d) Fe (e) C (graphite) (f) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3}\) (g) HCl (h) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\) (i) \(\mathrm{K}_{3} \mathrm{PO}_{4}\)

Ionic crystalline solids are a form of matter characterized by a high degree of order and a repeating pattern known as a crystal lattice structure. In ionic solids, the lattice is composed of positively charged cations and negatively charged anions, which are held together by the strong electrostatic forces of attraction known as ionic bonds. An example of an ionic crystalline solid is calcium chloride (CaCl_2), typically formed when a metal reacts with a nonmetal. The lattice energy, the released energy when the ions come together to form the solid, is a key indicator of the solid's stability and melting point. Ionic crystalline solids often have high melting points and are generally soluble in water due to the polarity of the water molecules which can surround and separate the ions.

Network covalent crystalline solids are materials where atoms are bonded covalently in a continuous network extending throughout the material. Unlike ionic solids, where the bond is between oppositely charged ions, network solids involve nonmetals that share electrons to form very strong covalent bonds. Examples include silicon carbide (SiC), and graphite, a form of carbon (C). These solids are extremely hard, have high melting points, and are typically poor conductors of electricity, with the exception of graphite, which can conduct electricity along the planes of carbon atoms. Because of the strength of the covalent bonds, network covalent solids are also resistant to high pressures and temperatures.

Molecular crystalline solids are composed of atoms or molecules held together by intermolecular forces, which are weaker than the ionic or covalent bonds found in other types of solids. Examples of these solids include solid nitrogen (N_2), butane (CH_3CH_2CH_2CH_3), and hydrochloric acid (HCl). Molecules in these solids are arranged in a lattice and the intermolecular forces include London dispersion forces, dipole-dipole interactions, and hydrogen bonding. Molecular solids typically have lower melting and boiling points compared to ionic or network covalent crystals, because the forces holding the molecules in place require less energy to overcome.

Metallic crystalline solids consist of metal atoms packed closely together in a crystal lattice. The defining feature of these solids is the presence of delocalized valence electrons that are not bound to any one atom but flow freely throughout the solid. This 'sea of electrons' is responsible for the high electrical and thermal conductivity of metals. An iron (Fe) crystal is a classic example of a metallic solid, exhibiting characteristics such as malleability and ductility. These metals can be pounded into thin sheets or drawn into wires, which is enabled by the ability of atoms to slide past each other without breaking the metallic bond.

The crystal lattice structure is a systematic, geometric arrangement of particles that extends in all three spatial dimensions. This structure can be thought of as the 'skeleton' of a crystalline solid, providing stability and defining its properties. Each point on the lattice, called a lattice point, represents the position of a particle, whether it's an atom, an ion, or a molecule. The smallest repeating unit of the lattice is called the unit cell, which repeats to form the solid. The shape and size of the unit cell depend on the forces between the particles and the way in which the particles pack together. By understanding the crystal lattice structure, scientists can predict and explain the physical properties of the solid, such as density, cleavage, and the angles between faces of crystals.