Solids come in various types, each with unique properties. Ionic and metallic solids have high melting points and conduct electricity well. Covalent and network solids differ in structure and melting points. Alloys combine metals for enhanced properties.

Ionic solids are held together by electrostatic forces, with lattice energy and crystal structure playing key roles. Metallic solids feature delocalized electrons, enabling conductivity and malleability. Both types adopt specific packing arrangements for stability and efficiency.

Types of Solids

Ionic and Metallic Solids

• Ionic solids form through electrostatic attraction between oppositely charged ions (NaCl)
• Metallic solids consist of metal atoms held together by metallic bonding (Cu, Fe, Al)
• Metallic bonding involves delocalized electrons moving freely through the lattice of positive metal ions
• Both ionic and metallic solids typically exhibit high melting points and electrical conductivity

Covalent and Network Solids

• Covalent solids comprise molecules held together by intermolecular forces (sugar, ice)
• Network solids feature extended three-dimensional structures of covalently bonded atoms (diamond, quartz)
• Covalent solids often have lower melting points compared to ionic or metallic solids
• Network solids possess extremely high melting points due to their extensive covalent bonding

Alloys and Composite Materials

• Alloys result from combining two or more metallic elements (brass, steel)
• Substitutional alloys replace some atoms in the crystal lattice with different metal atoms (bronze)
• Interstitial alloys incorporate smaller atoms into spaces between larger atoms in the lattice (steel)
• Alloys often exhibit enhanced properties compared to their constituent elements, such as increased strength or corrosion resistance

Ionic Solid Properties

Lattice Energy and Crystal Structure

• Lattice energy quantifies the strength of ionic bonds in a crystal structure
• Calculated as the energy required to separate one mole of a solid ionic compound into gaseous ions
• Factors affecting lattice energy include ion charge and ionic radius
• Higher lattice energy correlates with greater stability and higher melting points
• Crystal structures of ionic solids depend on the relative sizes and charges of the constituent ions

Madelung Constant and Electrostatic Interactions

• Madelung constant relates to the geometry of ions in a crystal lattice
• Accounts for the sum of all electrostatic interactions in an ionic solid
• Varies depending on the specific crystal structure (NaCl, CsCl, ZnS)
• Influences the overall stability and properties of ionic compounds
• Used in calculations of lattice energy and other crystal properties

Coordination Number and Packing Efficiency

• Coordination number represents the number of nearest neighbors for each ion in a crystal
• Determines the arrangement of ions in the crystal lattice
• Affects the overall stability and properties of the ionic solid
• Common coordination numbers include 4 (tetrahedral), 6 (octahedral), and 8 (cubic)
• Packing efficiency relates to how tightly ions are packed in the crystal structure
• Higher packing efficiency generally leads to increased density and stability

Metallic Solid Properties

Delocalized Electrons and Electrical Conductivity

• Delocalized electrons in metallic solids move freely throughout the crystal lattice
• Creates a "sea of electrons" surrounding the positively charged metal ions
• Enables high electrical conductivity in metallic solids
• Explains the malleability and ductility of metals
• Contributes to the thermal conductivity of metallic materials

Closest Packing and Crystal Structures

• Metallic solids often adopt closest packing arrangements to maximize density
• Common structures include body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP)
• BCC structure features atoms at the corners and center of a cubic unit cell (Fe, Cr, W)
• FCC structure has atoms at the corners and face centers of a cubic unit cell (Cu, Al, Ag)
• HCP structure consists of alternating layers of closely packed atoms (Mg, Zn, Co)
• Packing efficiency varies among these structures, with FCC and HCP being the most efficient