CHEMISTRY GLOSSARY

trigonal planar molecular geometry    →   trigonska planarna geometrija molekule

Trigonal planar is a molecular shape that results when there are three bonds and no lone pairs around the central atom in the molecule. The pairs are arranged along the central atom’s equator, with 120° angles between them. Molecules with an trigonal planar electron pair geometries have sp²d hybridization at the central atom. The carbonate ion (CO₃^2-) has a trigonal planar geometry.

trigonal pyramidal molecular geometry    →   trigonska piramidalna geometrija molekule

Trigonal pyramidal is a molecular shape that results when there are three bonds and one lone pair on the central atom in the molecule. Molecules with an tetrahedral electron pair geometries have sp³ hybridization at the central atom. Ammonia (NH₃) is a trigonal pyramidal molecule.

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).

acceptor    →   akceptor

Acceptor is a compound, molecule or ion, to which electrons are donated in the formation of a coordinate bond

activation energy    →   energija aktivacije

Activation energy (E_a) is the energy that must be added to a system in order for a process to occur, even though the process may already be thermodynamically possible. In chemical kinetics, the activation energy is the height of the potential barrier separating the products and reactants. It determines the temperature dependence on the reaction rate.

active site    →   aktivno mjesto

Active site is a pocket or crevice on an enzyme molecule that fits reactant molecules like a hand in a glove. The active site lowers the activation energy for reaction

AMU    →   AMU

AMU or atomic mass unit is a unit of mass used to express relative atomic masses. It is equal to 1/12 of the mass of an atom of the isotope carbon-12 and is equal to 1.66 033×10^-27 kg. This unit superseded both the physical and a chemical mass unit based on oxygen-16 and is sometimes called the unified mass unit or the dalton.

anisotropy    →   anizotropija

Anisotropy is the property of molecules and materials to exhibit variations in physical properties along different molecular axes of the substance.

atomic clock    →   atomski sat

Atomic clock is an apparatus for standardizing time based on periodic phenomena within atoms or molecules (ammonia clock; caesium clock).

Avogadro, Amadeo    →   Avogadro, Amadeo

Amadeo Avogadro (1776-1856) is an Italian chemist and physicist that proposed a correct molecular explanation for Gay-Lussac’s law of combining volumes. His work provided a simple way to determine atomic weights and molecular weights of gases. He is published a theory about the movement of particles in gases that became known as Avogadro’s Law.