P

p block para
paramagnetic partial pressure
pascal Pauli exclusion principle
peptide peptide bond
percent ionization period
periodic table pH
phase diagram photon
phototube detector physical change
physical property pi bond
pK Planck's constant
pOH polar
polarizability pollution
polyatomic polymer
polymerization polymorphism
polypeptide polyprotic
polysaccharide positional isomer
positron potentiometer
precipitation precision
pressure primary structure
product protein
proton pseudo-first-order reaction
pyrophoric  




p block

Columns 13 through 18 of the periodic table, containing elements in the periodic table over which the p atomic orbitals are being filled.


para

Describing the relationship between two groups attached to carbon atoms on a benzene-like ring that have two carbon atoms between them.


paramagnetic

Describing a substance containing unpaired electrons that is attracted by a magnetic field.


partial pressure

That portion of the total pressure of a mixture of gases contributed by the presence of one of the component gases.


pascal

The SI unit for pressure, equal to a kg/s2m


Pauli exclusion principle

The statement that no two electrons in an atom can have the same set of quantum numbers; the principle leads to the rule that only two electrons (having opposite spin) can occupy an atomic orbital.


peptide

A molecule of two or more amino acids joined by amide linkages or "peptide bonds."


peptide bond

The amide linkage that joins the carboxylic acid end of one amino acid with the amino end of another amino acid to form a peptide or protein.


percent ionization

The fraction (expressed as a percent) of an electrolyte that dissociates into ions; this fraction depends upon both the value of the equilibrium constant and the concentration of the species that is dissociating.


period

Those elements from a single column of the periodic table.


periodic table

A chart showing the symbols of the elements arranged in order by atomic number and having chemically related elements appearing in columns.


pH

A logarithmic measure of the concentration of hydrogen ion expressed as -log10([H+]).


phase diagram

A diagram showing conditions, most typically of pressure and temperature, under which different phases of a substance exist at equilibrium.


photon

A quantum of energy from electromagnetic radiation; the value of the energy available is the product of the frequency of light and Planck's constant.


phototube detector

The phototube detector converts light energy to an electrical signal. The intensity of light can be measured with the phototube detector.


physical change

A process in which the identity of substances remains unchanged.


physical property

A characteristic of a material that can be measured without changing the material's chemical composition.


pi bond

A bond in which the electron density lies above and below a plane containing the bonded atoms; formed by the overlap of two p orbitals or a p orbital and a d orbital.


pK

A logarithmic measure of the value of the equilibrium constant expressed as -log10([K]).


Planck's constant

A proportionality constant between the energy of a photon of light and the frequency of that light; equal to 6.6261 x 10-34 J sec


pOH

A logarithmic measure of the concentration of hydroxide ion expressed as -log10([OH-]).


polar

Describing a molecule having a separation of centers of positive and negative electrical charge that makes the molecule assume certain orientations more than others in an electric field.


polarizability

The ability of the electrons in a species to change position in response to the presence of an outside electrical field.


pollution

The contamination of the air, water, and earth by personal, industrial, and farm waste.


polyatomic

Containing two or more atoms.


polymer

A large molecule containing a large number of repeating units; a substance formed from such molecules.


polymerization

The process of forming a polymer from monomers.


polymorphism

The ability of a substance to exist in more than one crystalline form.


polypeptide

A polymer of many amino acids joined by amide linkages or "peptide bonds."


polyprotic

Describing an acid that can donate two or more hydrogen ions ("protons") to a base.


polysaccharide

A polymer of many units, each of which is a carbohydrate.


positional isomer

One of two or more compounds that have the same chemical composition but that differ in the location at which functional groups are attached to the backbone of atoms.


positron

A positively charged particle having the same mass as an electron.


potentiometer

An instrument for measuring the voltage of a system by opposing that voltage until no current flows.


precipitation

The formation of a solid within a solution, often by the combination of cations and anions to form an insoluble ionic compound.


precision

The extent of agreement among several experimental values.


pressure

Force per unit area; in gases arising from the effect of collisions by the molecules of the gas with the wall of the container.


primary structure

The sequence of amino acids that defines a protein.


product

A substance produced by a chemical reaction.


protein

A biological polymer of amino acids joined by peptide bonds.


proton

The positively charged particle in an atomic nucleus; its mass is similar to the mass of a hydrogen atom.


pseudo-first-order reaction

A reaction in which the concentrations of reactants are such that the reaction appears to depend directly upon the concentration of one reactant; the concentrations of other reactants change so little as to affect the rate only negligibly.


pyrophoric

Igniting spontaneously when exposed to air.



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