CHEMISTRY GLOSSARY

molar absorption coefficient    →   molarni apsorpcijski koeficijent

Molar absorption coefficient (ε) is the absorption coefficient divided by amount-of-substance concentration of the absorbing material in the sample solution (ε = a/c). The SI unit is m²mol^-1. Also called extinction coefficient, but usually in units of dm³cm^-1mol^-1.

crystal system    →   kristalni sustav

Crystal system is a method of classifying crystalline substances on the basis of their unit cell. There are seven unique crystal systems. The simplest and most symmetric, the cubic (or isometric) system, has the symmetry of a cube. The other six systems, in order of decreasing symmetry, are hexagonal, tetragonal, rhombohedral (also known as trigonal), orthorhombic, monoclinic and triclinic.

Crystal system	Unit-cell	Conditions on unit-cell edges and angles
cubic		a=b=c α=β=γ=90°
hexagonal		a≠c α=γ=90° β=120°
tetragonal		a=b≠c α=β=γ=90°
rhombohedral		a=b=c α=β=γ≠90°
orthorhombic		a≠b≠c α=β=γ=90°
monoclinic		a≠b≠c α=γ=90°≠β
triclinic		a≠b≠c α≠β≠γ≠90°

monomer    →   monomer

Monomer is a simple molecule which is capable of combining with a number of like or unlike molecules to form a polymer. Monomer is repeating structure unit within a polymer.

nautical mile    →   morska milja

Nautical mile is a legal international unit of length temporarily maintained with the SI. It is still used in navigation (merchant marine, aviation). It is equal to the length of an arc of one minute measured at a latitude of N 45° (mile = 1852 m). The international nautical mile has been taken equal to the nautical mile.

dipole moment    →   dipolni moment

Electric dipole moment (μ) is a product of the positive charge and the distance between the charges. Dipole moments are often stated in debyes; The SI unit is the coulomb metre. In a diatomic molecule, such as HCl, the dipole moment is a measure of the polar nature of the bond; i.e. the extent to which the average electron charges are displaced towards one atom (in the case of HCl, the electrons are attracted towards the more electronegative chlorine atom). In a polyatomic molecule, the dipole moment is the vector sum of the dipole moments of the individual bonds. In a symmetrical molecule, such as tetrafluoromethane (CF₄) there is no overall dipole moment, although the individual C-F bonds are polar.

electric field    →   električno polje

If a small amount of charge experience a force, there is an electric field in the vicinity. Electric field E is defined in terms of electrostatic force F that would be exerted on positive test charge q_p placed in the field:

SI unit for electric field is N C^-1, or V m^-1.

The electric field due to a point charge q at distance r from it given by:

where ε₀ is permittivity constant, and is ε_o=8.85×10^-12 C² N^-1 m^-2.

electron affinity    →   elektronski afinitet

Electron affinity (E_A) is the energy change occurring when an atom or molecule gains an electron to form a negative ion. For an atom or molecule X, it is the energy released for the electron-attachment reaction

This is often measured in electronvolts. Alternatively, the molar enthalpy change, ΔH, can be used.

oersted    →   ersted

Oersted (Oe) is a non-SI unit of magnetic field (H), equal to 79.577 471 57 A/m. The unit was named after the Danish physicist and chemist Hans Christian Oersted (1777-1851).

ohm    →   om

Ohm (Ω) is the SI derived unit of electric resistance. The ohm is the electric resistance between two points of a conductor when a constant difference of potential of one volt, applied between these two points, produces in this conductor a current of one ampere, this conductor not being the source of electromotive force (Ω = V/A). The unit was named after the German physicist Georg Simon Ohm (1789-1854).

oligomer    →   oligomer

Oligomer is a substance consisting of molecules of intermediate relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetitions of units derived, actually or conceptually, from molecules of low relative molecular mass. In contrast to a polymer, the properties of an oligomer can vary significantly with the removal of one or a few of its units.