CHEMISTRY GLOSSARY

lead    →   olovo

Lead has been known since ancient times. The origin of the name comes from the Latin word plumbum meaning liquid silver. It is very soft, highly malleable and ductile, blue-white shiny metal. Tarnishes in moist air; stable in oxygen and water. Dissolves in nitric acid. Compounds toxic by inhalation or ingestion. Danger of cumulative effects. Lead is found most often in ores called galena or lead sulfide (PbS). Used in solder, shielding against radiation and in batteries.

lead-acid battery    →   olovni akumulator

Lead-acid battery is a electrical storage device that uses a reversible chemical reaction to store energy. It was invented in 1859 by French physicist Gaston Planté. Lead-acid batteries are composed of a lead(IV) oxide cathode, a sponge metallic lead anode and a sulphuric acid solution electrolyte.

In charging, the electrical energy supplied to the battery is changed to chemical energy and stored. The chemical reaction during recharge is normally written:

In discharging, the chemical energy stored in the battery is changed to electrical energy. During discharge, lead sulfate (PbSO4) is formed on both the positive and negative plates. The chemical reaction during discharge is normally written:

Lead acid batteries are low cost, robust, tolerant to abuse, tried and tested. For higher power applications with intermittent loads however, they are generally too big and heavy and they suffer from a shorter cycle life.

leucine    →   leucin

Leucine is hydrophobic amino acids with aliphatic side chain. It has one additional methylene group in its side chain compared with valine. The nonpolar hydrophobic amino acids tend to cluster together within proteins, stabilizing protein structure by means of hydrophobic interactions. Leucine is an essential amino acid, which means that humans cannot synthesize it, so it must be ingested.

• Abbreviations: Leu, L
• IUPAC name: 2-amino-4-methylpentanoic acid
• Molecular formula: C₆H₁₃NO₂
• Molecular weight: 131.17 g/mol

Lewis structure    →   Lewisova struktura

Lewis structure is the representation of the electron arrangement in atoms, ions, or molecules by showing the valence electrons as dots placed around the symbols for the elements.

Lewis symbols    →   Lewisovi simboli

Lewis symbols are the shorthand electron dot structure of an atom.

Liebig condenser    →   Liebigovo hladilo

Liebig condenser is used for condensing of vapours that pass trough the centre tube. It is cooled with water that passes in the outer tube (shell around the centre tube) in the opposite direction than the one of hot vapour. Though named after the German chemist Justus von Liebig (1803-1873), he cannot be given credit for having invented it because it had already been in use for some time before him.

ligand    →   ligand

Ligand is an ion (F^-, Cl^-, Br^-, I^-, S^2-, CN^-, NCS^-, OH^-, NH₂^-) or molecule (NH₃, H₂O, NO, CO) that donates a pair of electrons to a metal atom or ion in forming a coordination complex. The main way of classifying ligands is by the number of points at which they are attached to, or bound to, the metal center. This is the denticity. Ligands with one potential donor atom are monodentate. Polydentate ligand is a ligand that is attached to a central metal ion by bonds from two or more donor atoms. Ligands with more than one potential donor atom are known as ambidentate, such as the thiocyanate ion, NCS-, which can bind to the metal center with either the nitrogen or sulphur atoms. Chelating ligands are those polydentate ligands which can form a ring including the metal atom.

light    →   svjetlo

Light (visible radiation) is a form of electromagnetic radiation able to be detected by the human eye. Its wavelength range is between about 400 nm and about 700 nm. The boundaries are not precise, because individuals vary in their ability to detect extreme wavelengths.

lime    →   živo vapno

Lime (or quicklime) is the common name for calcium oxide (CaO). It is manufactured from limestone, CaCO₃, by heating it to a high temperature (about 1 000 °C). At this temperature carbon dioxide, CO₂, is released from the limestone creating calcium oxide, CaO.

A further process involves adding water in a process known as hydrating, which produces hydrated, or slaked lime [Ca(OH)₂].

limestone    →   vapnenac

Limestone is a sedimentary rock composed primarily of calcium carbonate in the form of the mineral calcite.. Some 10 % to 15 % of all sedimentary rocks are limestones. Limestone is usually organic, but it may also be inorganic. Calcium carbonate may have been directly precipitated from the sea-water or by the lithification of coral reefs, marine organism shells, or marine organism skeletons.