Coarse particles (PM10) have diameters between 1 x 10^-5 m and 2.5 x 10^-6 m and are often referred to as dust
Conductor: a material containing charged particles free to move to carry electrical or thermal energy
Covalent bond: a shared pair of electrons between two non-metals
Diamond: a giant covalent structure made up of carbon atoms, each forming four covalent bonds with four other carbon atoms
Electrostatic forces: the strong forces of attraction between oppositely charged ions
Empirical formula: the smallest whole number ratio of atoms of each element in a compound
Fine particles (PM2.5) have diameters between 100 and 2500 nm and are often referred to as fine dust
Fullerenes are molecules of carbon atoms with hollow shapes, based on hexagonal rings of carbon atoms but may also contain rings with five or seven carbon atoms
Gas: the state of matter where particles have the most energy, are relatively spread out, and move randomly in all directions
Graphene: a single layer of graphite with properties useful in electronics and composites
Graphite: a giant covalent structure made up of carbon atoms, each forming three covalent bonds with three other carbon atoms, forming layers of hexagonal rings with no covalent bonds between the layers
Ion: an atom or molecule with an electric charge due to the loss or gain of electrons
Ionic bond: formed when a metal atom loses electron(s) to form a positively charged ion and a non-metal gains these electron(s) to form a negatively charged ion
Ionic compound: a chemical compound formed of ions, held together by strong electrostatic forces
Intermolecular forces: forces between molecules impacting physical properties like boiling/melting point
Lattice: a repeating regular arrangement of atoms/ions/molecules, occurring in crystal structures
Liquid: the state of matter where particles are arranged randomly and close together, able to move past each other
Metallic bond: bonds present in metals between positive metal ions and negatively charged electrons
Metals: elements reacting to form positive ions, found to the left and towards the bottom of the periodic table
Molecular formula: the actual ratio of atoms of each element present in a compound
Nanoparticles: have diameters between 1 nm to 100 nm and can exhibit properties different from the same material in bulk
Nanoscience: refers to structures that are 1–100 nm in size, of the order of a few hundred atoms
Particle theory: models the three states of matter by representing particles as small solid spheres, explaining melting, boiling, freezing, and condensing
Polymers: large long-chain molecules made up of small monomers joined by covalent bonds
Repeat unit: the part of a polymer whose repetition would produce the complete polymer chain
Solid: the state of matter where particles hold a regular arrangement and have the least amount of energy
State symbols: symbols in chemicalequations denoting the states of the chemicals reacting: (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous solution