Question

What kinds of forces hold each of the three basic categories of atomic solids together?

Short answer

Atomic solids are held together by metallic bonds in metallic solids, ionic bonds in ionic solids, and covalent bonds in covalent network solids.

Step-by-step solution

Identifying the Three Basic Categories of Atomic Solids

Atomic solids can be categorized into three basic types based on the forces that hold the atoms together: metallic solids, ionic solids, and covalent network solids. Each type is held together by different kinds of forces.

Metallic Solids

Metallic solids are held together by metallic bonds. In these bonds, the valence electrons are delocalized and flow freely between the positively charged metal ions, forming a 'sea of electrons.' The attraction between the electrons and the metal cations holds the structure together.

Ionic Solids

Ionic solids are held together by ionic bonds, which are electrostatic attractions between oppositely charged ions. These occur when electrons are transferred from a metal atom to a non-metal atom, creating cations and anions that are held together by their opposite charges.

Covalent Network Solids

Covalent network solids are held together by covalent bonds where atoms share electrons to achieve a full valence shell. These solids have a network structure of strong covalent bonds that result in high melting points and hardness.

Key concepts

Metallic Solids

Imagine entering a room where everyone is freely sharing their possessions; this scenario is somewhat analogous to the structure of metallic solids. In metallic solids, the atoms release their valence electrons into a communal 'sea' that permeates the entire structure. This diffusion of electrons allows the metal atoms to slide past one another easily, which explains the malleability and ductility—properties that allow metals to be shaped into wires or sheets—characteristic of these materials.

The Metallic Bond

The bond holding metallic solids together is unique; it involves the attraction between free-flowing valence electrons and the positively charged metal ions they surround. This metallic bond is responsible for the electron flow that gives rise to electrical conductivity and the ability of metals to conduct heat efficiently. Despite the free movement of electrons, the electrostatic attraction within the 'sea' is sufficiently robust to hold the structure intact, providing stability to the metallic solid.

Properties of Metallic Solids

Metallic solids also exhibit a lustrous appearance, another trait attributable to the free electrons which can absorb and release photons, contributing to the metals' reflectivity. When discussing metallic solids, one must consider the role of alloys—these are formed when different metal elements are mixed, enhancing certain properties such as strength, resistance to corrosion, or lowering the melting point, depending on the application desired.

Ionic Solids

Ionic solids can be thought of as a societal model of strict give-and-take, where each participant either donates or receives something to maintain stability. Indeed, ionic solids are the epitome of organized structural integrity, as they are composed of alternating positive and negative ions, which adhere strictly to an ordered, crystalline arrangement. This strict geometric configuration owes its existence to the ionic bonds created when electrons are transferred from metal atoms to non-metal atoms.

Electrostatic Forces in Ionic Bonds

The entirety of an ionic solid is essentially a grand mosaic of ions clasped together by the unseen hand of electrostatic attraction. These ionic bonds ensure that each cation (positive ion) is surrounded by anions (negative ions), and vice versa. This maximizes the attractive forces and minimizes repulsion, resulting in a crystalline lattice that is rigid and tough.

Characteristic Properties of Ionic Solids

Due to these bonds, ionic solids are known for characteristics such as high melting points and hardness, reaffirming their stability. They are generally poor conductors of electricity as solids because the ions are not free to move; however, upon melting or dissolving in water, they can conduct electrical current as the ions become mobile. It's not all about sturdiness though—ionic compounds can be brittle, and under pressure, their layers may shift in a way that aligns like charges, leading to repulsion and the potential shattering of the structure.

Covalent Network Solids

In covalent network solids, we delve into a network where each individual is committed to sharing equally and indefinitely with their neighbors. These solids are a maze of covalent bonds, formidable and directional in nature, linking atoms in a continuous network. This bonding is derived from the robust sharing of electrons between two non-metal atoms to achieve full valence shells.

Strength of Covalent Bonds

The strength of covalent bonds in network solids is impressive, dictating their defining qualities: high melting points, significant hardness, and often transparency to visible light. Examples like diamond and quartz epitomize these attributes through their structure; each carbon atom in diamond is tetrahedrally bonded to four others, creating an extremely sturdy and stiff lattice.

Diverse Properties and Applications

Despite the strong internal bonds, covalent network solids do not conduct electricity in their pure, non-doped state as they lack free charge carriers. However, under certain conditions, semiconductors like silicon can bridge the electrical divide through doping—introducing impurities to create charge carriers. Furthermore, the hardness of materials like diamond makes them ideal for cutting tools, while the thermal resistance of silicon carbide can be exploited in high-temperature applications.