Key Terms

• 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 chemical equations denoting the states of the chemicals reacting: (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous solution