An arrangement of elements in order of increasing atomic numbers that also emphasizes periodicity.
Peroxide
A compound containing oxygen in the -1 oxidation state. Metal peroxides contain the peroxide ion, O22-
pH
Negative logarithm of the concentration (mol/L) of the H3O+[H+] ion; scale is commonly used over a range 0 to 14.
Phase Diagram
Diagram that shows equilibrium temperature-pressure relationships for different phases of a substance.
Phenol
Hydrocarbon derivative containing an [OH] group bound to an aromatic raing.
Photochemical Oxidants
Photochemically produced oxidizing agents capable of causing damage to plants and animals.
Photochemical Smog
A brownish smog occurring in urban areas receiving large amounts of sunlight; caused by photochemical (light-induced) reactions among nitrogen oxides, hydrocarbons and other components of polluted air that produce photochemical oxidants.
Photoelectric Effect
Emission of an electron from the surface of a metal caused by impinging electromagnetic radiation of certain minimum energy; current increases with increasing intensity of radiation.
Photon
A packet of light or electromagnetic radiation; also called quantum of light
Physical Change
A change in which a substance changes from one physical state to another but no substances with different composition are formed. Example Gas to Liquid - Solid.
Plasma
A physical state of matter which exists at extremely high temperatures in which all molecules are dissociated and most atoms are ionized.
Polar Bond
Covalent bond in which there is an unsymmetrical distribution of electron density.
Polarimeter
A device used to measure optical activity.
Polarization
The buildup of a product of oxidation or a reduction of an electrode, preventing further reaction.
Polydentate
Refers to ligands with more than one donor atom.
Polyene
A compound that contains more than one double bond per molecule.
Polymerization
The combination of many small molecules to form large molecules.
