CHEMISTRY GLOSSARY

wave-particle duality    →   valno-čestična dualnost

Wave-particle duality is an observation that electrons, photons, and other very small entities behave like particles in some experiments and like waves in others.

wavefunction    →   valna funkcija

Wavefunction (Ψ) is a mathematical function that gives the amplitude of a wave as a function of position (and sometimes as a function of time and/or electron spin). Wavefunctions are used in chemistry to represent the behaviour of electrons bound in atoms or molecules.

wavelength    →   valna duljina

Wavelength is the distance between two neighbouring peaks of the electromagnetic wave.

wavenumber    →   valni broj

Wavenumber is the number of wave cycles per unit distance.

There are unfortunately two different definitions of the wavenumber.

Wavenumber, k, is most frequently defined as

with wavelength λ, phase velocity of wave v_p, and angular frequency ω.

Less frequently it is defined simply as

One must be careful to note which definition is in use. Wavenumbers are used extensively in infrared spectroscopy, and usually have units of cm^-1.

absorbance    →   apsorbancija

Absorbance (A) is a logarithm of the ratio of incident radiant power (P_o) to transmitted radiant power (P) through a sample (excluding the effects on cell walls).

The absorption of light by a substance in a solution can be described mathematically by the Beer-Lambert law

where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol^-1 cm^-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L^-1).

absorptance    →   apsorptancija

Absorptance (α) is the ratio of the radiant or luminous flux in a given spectral interval absorbed in a medium to that of the incident radiation. Also called absorption factor.

angstrom    →   angstrem

Ångström (Å) is a unit of length equal to 10^-10 m. The Ångström is defined in terms of the wavelength of the emission spectra’s red line of an atom of cadmium (6438.4696 Å).

atomic absorption spectroscopy    →   atomska apsorpcijska spektroskopija

Atomic absorption spectroscopy (AAS) An analytical technique in which a sample is vapourised and the nonexcited atoms absorb electromagnetic radiation at characteristic wavelengths.

atomic orbital    →   atomska orbitala

Atomic orbital is a wave function that describes the behaviour of an electron in an atom.

Beer’s law    →   Beerov zakon

Beer’s law (or Beer-Lambert law) is the functional relationship between the quantity measured in an absorption method (A) and the quantity sought, the analyte concentration (c). As a consequence of interactions between the photons and absorbing particles, the power of the beam is attenuated from P_o to P. Beer’s law can be written

where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol^-1 cm^-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L^-1).