Types of Solids SCH 4U1

Types of Solids We will classify solids into four types: Ionic Solids Metallic Solids Molecular Solids (Non Polar and Polar) Covalent network solids (3D and 2D)

Ionic Solids An ionic solid is a solid that consists of cations and anions (Latice point particles) held together by the electrical attraction of opposite charges (ionic bonds) This is technically considered an intra-ion , 3D force, and results in ionic compounds having very high melting points as a great amount of energy is required to separate the ions.

Ionic Solids con’t Most are water soluble due to the formation of ion-dipole attractions. These solutions are electrolytes, as the ions are mobile. Can form basic and acid solutions. No conductivity in solid form as the ions are in fixed lattice positions. Can be magnetic if solid contains Fe, Co or Ni ions.

Arrangement of Ions in a Sodium chloride crystal

Metallic solids In metals, the valence electrons of neighbouring positive kernals form a sort of ‘electron sea’ These electrons are called “delocalized electrons” This ‘delocalized electron soup’ can be thought of as a ‘glue’ that holds the positive nuclei of the metal atoms together. The metallic bond.

Metallic solids Metals usually have high melting points, although this can be highly variable. Conduct heat and electricity due to mobile electrons. Can be magnetic is made of Fe, Co or Ni. Insoluble in water.

Different Types of Crystal Lattices

Gallium

Molecular solids A molecular solid is a solid that consists of atoms or molecules held together by intermolecular forces Examples include: Solid neon (melting point of -248oC) Solid CO2 (dry ice) Solid H2O (ice) Iodine Sugar

Molecular solids – Non-polar I2 is non-polar, so it has only London Dispersion forces However, it has 106 electrons, giving it sufficient IMF to be a solid at room temperature. Weak IMF leads to lowest melting points. No mobile electrons, so no electrical conductivity Insoluble in water due to lack of polarity.

Molecular solids - Polar Have stronger IMFs of dipole- dipole forces and Hydrogen Bonding forces. Same electrical properties as non- polar. Both water solubility and melting points are greater. Can form acidic or basic solutions.

Covalent Network Solid - 3D Highest melting point as all atoms are covalently bonded. Hard, generally crystalline or “glassy” appearance No water solubility No electrical or heat conductivity.

Silica glass (SiO2)

Amethyst quartz (SiO2)

Graphite - 2D network solid It consists of ‘sheets’ of covalently bonded atoms It has a melting point lower than 3D, they are softer and usually shiny It is also an electrical conductor in one direction only because of delocalized electrons between sheets of atoms. Insoluble in water.

Graphite, Diamond and Silicon dioxide (Silica)