CHEMISTRY GLOSSARY

chemisorption    →   kemisorpcija

Chemisorption is a binding of a liquid or gas on the surface or in the interior of a solid by chemical bonds or forces.

collagen    →   kolagen

Collagen is a polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin. Collagen is the primary organic constituent of bone, cartilage, and connective tissue (becomes gelatine through boiling).

aromatic compounds    →   aromatski ugljikovodici

Aromatic compounds are a major group of unsaturated cyclic hydrocarbons containing one or more rings, typified by benzene, which has a 6-carbon ring containing three double bonds. All the bonds in benzene (C₆H₆) are the same length intermediate between double and single C-C bonds. The properties arise because the electrons in the p-orbitals are delocalised over the ring, giving extra stabilization energy of 150 kJ/mol over the energy of Kekulé structure. Aromatic compounds are unsaturated compounds, yet they do not easily partake in addition reactions.

Historical use of the term implies a ring containing only carbon (e.g., benzene, naphthalene), but it is often generalized to include heterocyclic structures such as pyridine and thiophene.

arsenic    →   arsen

Arsenic was discovered by Albertus Magnus (Germany) in 1250. The origin of the name comes from the Greek word arsenikon meaning yellow orpiment. It is steel-grey, brittle semi-metal. Resists water, acids and alkalis. Tarnishes in air, burns in oxygen. Highly toxic by inhalation or ingestion. Arsenic is found in mispickel (arsenopyrite). Many of its compounds are deadly poison and used as weed killer and rat poison. Used in semiconductors. Some compounds, called arsenides, are used in the manufacture of paints, wallpapers and ceramics.

asparagine    →   asparagin

Asparagine is neutral amino acids with polar side chains. The polar amino acids are an important class of amino acids since they provide many of the functional groups found in proteins. Asparagine is a common site for attachment of carbohydrates in glycoproteins. In general this is not very reactive residues. Asparagine is amide derivative of aspartic acid. Asparagine is not essential for humans, which means that it can be synthesized from central metabolic pathway intermediates and is not required in the diet.

• Abbreviations: Asn, N
• IUPAC name: 2,4-diamino-4-oxobutanoic acid
• Molecular formula: C₄H₈N₂O₃
• Molecular weight: 132.12 g/mol

covalent compound    →   kovalentni spoj

Covalent compound is a compound made of molecules - not ions, such as H₂O, CH₄, Cl₂. The atoms in the compound are bound together by shared electrons. Also called a molecular compound.

covalentity    →   kovalentnost

Covalentity is a maximum number of covalent bond that one atom can make, it is equal to the number of hydrogen atoms that are combined with other atoms. It is usually constant.

cyanide process    →   cijanidni postupak

Cyanide process is a method for separating a metal from an ore. Crushed ore is treated with cyanide ion to produce a soluble metal cyanide complex. The complex is washed out of the ore and reduced to metallic form using an active metal (usually zinc).

artificial radioactive isotope    →   umjetni radioaktivni izotop

Artificial radioactive isotopes are formed when an atom is bombed with an accelerator or exposing it to slow moving neutrons in a nuclear reactor. In this way isotopes (radionuclides) are obtained which are non-existent in nature because of their unstability and radioactive transition into stable isotopes. Most important radioactive isotopes are:

Radioactive isotope of cobalt is formed when ordinary metal cobalt is bombed with neutrons in a nuclear reactor.

Radioactive isotope of phosphorus is formed when ordinary phosphorus is bombed with deuterons produced in cyclotron.

radioactive isotope of carbon is formed when a nitrogen is bombed with slow moving neutrons in a nuclear reactor. It is mostly used as a radioactive indicator.

atom radius    →   radijus atoma

Atoms and molecules have no strict boundaries. The volume of a free atom is usually defined as that volume that contains 90 % of electron cloud. The radius of an atom represents half of interatom distance of two identical atoms which are in touch but are not interconnected either by a covalent or an ionic bond, but with a very weak van der Waals’s bond.