CHEMISTRY GLOSSARY

Biot-Savart law    →   Biot-Savartov zakon

The magnetic field B due to a current-carrying conductor can be determined by Biot-Savart law. The contribution to magnetic field set up at distance r by the current element IdL is given by expression:

where μ₀ is permeability constant. It plays a role in magnetic problems equivalent to the role of permittivity constant μ₀ in electrostatics problems. In order to obtain B, contributions of all current elements have to be integrated. In case of a long straight conductor, carrying current I, Biot-Savart law gives:

SI unit for magnetic field B is tesla (T).

Permaeability constant μ₀ has value 4π×10^-7 T m A^-1.

chemical compound formula    →   formula kemijskog spoja

Chemical elements are represented by their symbols, and chemical compounds are represented by a group of symbols of those elements from which the compound is composed. That group of symbols, which shows which atoms and in which number relation they are present in certain compound is called a chemical compound formula.

In a formula chemical symbols show which element is present in a certain compound, and its index shows how much of that element there is in a certain compound. From sulphuric acid formula H₂SO₄ we can see that one molecule of sulphuric acid consists of two atoms of hydrogen, one atom of sulphur and four atoms of oxygen.

einsteinium    →   einsteinij

Einsteinium was discovered by Albert Ghiorso (USA) in 1952. Named in honour of Albert Einstein (1879-1955). It is synthetic radioactive metal. Einsteinium was made by bombarding uranium with neutrons.

fermium    →   fermij

Fermium was discovered by Albert Ghiorso (USA) in 1953. Named in honour of Enrico Fermi. It is synthetic radioactive metal. Fermium was produced by bombarding lighter transuranium elements with still lighter particles or by neutron capture.

Born-Haber cycle    →   Born-Haberov kružni proces

Born-Haber cycle is a cycle of reactions used for calculating the lattice energies of ionic crystalline solids. For a compound MX, the lattice energy is the enthalpy of the reaction

The standard enthalpy of formation of the ionic solid is the enthalpy of the reaction

The cycle involves equating this enthalpy (which can be measured) to the sum of the enthalpies of a number of steps proceeding from the elements to the ionic solid. The steps are:

1) Atomization of the metal

2) Atomization of the nonmetal

3) Ionisation of the metal

This is obtained from the ionisation potential.

4) Ionisation of the nonmetal

This is electron affinity.

5) Formation of the ionic solids

Equation of the enthalpies gives

from which ΔH_L can be found.

cross-linking    →   umrežavanje

Cross-linking is an attachment of two chains of polymer molecules by bridges, composed of either an element, a group, or a compound, that join certain carbon atoms of the chains by primary chemical bonds, as indicated in the schematic diagram

Cross-linking occurs in nature in substances made up of polypeptide chains that are joined by the disulfide bonds of the cysteine residue, as in keratins or insulin. Cross-linking can be artificially effected, either adding a chemical substance (cross-linking agent), or by subjecting the polymer to high-energy radiation. Examples are: vulcanisation of rubber with sulphur, cross-linking of polystyrene with divinylbenzene, or cross-linking of polyethylene by means of high-energy radiation.

Cross-linking has the effect of changing a plastic from thermoplastic to thermosetting. Thus, it also increases strength, heat and electrical resistance, and especially resistance to solvents and other chemicals.

geochemistry    →   geokemija

Geochemistry is the scientific study of the chemical composition of the Earth. It includes the study of the abundance of the Earth’s elements and their isotopes and the distribution of the elements in environments of the Earth (lithosphere, atmosphere, biosphere, and hydrosphere).

heat of formation    →   toplina nastajanja

Heat of formation or enthalpy of is formation the heat evolved or absorbed when one mole of a compound is formed in its standard state from its constituent elements.

heterocyclic compounds    →   heterociklički spojevi

Heterocyclic compounds are cyclic compounds having as ring members atoms of at least two different elements, e.g., quinoline, 1,2-thiazole.

inorganic chemistry    →   anorganska kemija

Inorganic chemistry, the branch of chemistry concerned with compounds of elements other than carbon. Certain simple carbon compounds, such as CO, CO₂, CS₂, carbonates CO₃^2- and cyanides CN^-, are usually treated in inorganic chemistry.