CHEMISTRY GLOSSARY

Onsager relations    →   Onsagerove relacije

Onsager relations are an important set of equations in the thermodynamics of irreversible processes. They express the symmetry between the transport coefficients describing reciprocal processes in systems with a linear dependence of flux (J_i) on driving forces (X_j).

In Onsager’s theory the coupling coefficients are equal, L_ij = L_ji. This is known as reciprocal relations. The theory was developed by the Norwegian chemist Lars Onsager (1903-1976) in 1931.

quantum chemistry    →   kvantna kemija

Quantum chemistry is a theoretical branch of chemistry that concerns the application of quantum mechanics to chemical problems.

radioactivity    →   radioaktivnost

Radioactivity is capability of a spontaneous decay of an atom. In this way a new atom type is formed and radioactive radiation is released. An atom can emit three types of radioactive radiation: positive α-radiation, negative β-radiation and electrically neutral γ-radiation. During radioactive decay one element never emits all types of radiation at the same time.

orbital    →   orbitala

Orbital is the area in space about an atom or molecule in which the probability of finding an electron is greatest.

The possible atomic orbitals correspond to subshells of the atom. Thus there is one s-orbital for each shell (orbital quantum number l = 0). There are three p-orbitals (corresponding to the three values of l) and five d-orbitals. The shapes of orbitals depend on the value of l.

period    →   perioda

Periods are horizontal rows in the periodic table, each period begin with an alkali metal (one electron in the outermost principal quantum level) and ending with a noble gas (each having eight electrons in the outermost principal quantum level, except for helium, which is limited to two).

periodic table of the elements    →   periodni sustav elemenata

Periodic table is a table of elements, written in sequence in the order of atomic number or atomic weight and arranged in horizontal rows (periods) and vertical columns (groups) to illustrate the occurrence of similarities in the properties of the elements as a periodic function of the sequence. The original form was proposed by Dmitri Mendeleev (1834-1907) in 1869, using relative atomic masses.

pi bond    →   pi veza

Pi bonds (π bond) between atoms are formed by the side-on overlap of the atomic orbitals on the different atoms.

standard mean ocean water    →   standardna prosječna oceanska voda

Standard mean ocean water (SMOW) is a standard sample of pure water of accurately known isotopic composition which is maintained by the International Atomic Energy Agency. It is used for precise calibration of density and isotopic composition measurements.

transuranium element    →   trasuranski element

Transuranium elements are elements with an atomic number higher than 92 (uranium’s atomic number). Transuranium elements are unstable and occur in extremely low concentrations in nature. Most are made artificially.

proton    →   proton

Proton is a stable elementary particle of unit positive charge and spin 1/2. Protons and neutrons, which are collectively called nucleons, are the constituents of the nucleus.

In 1886, German physicist Eugene Goldstein (1850-1930) discovered positive particles by using a modified Crookes tube with holes in the cathode in an evacuated tube. When cathode rays were given off in one direction toward the anode, other rays found their way through the holes in the cathode and sped off in the opposite direction. Since these other rays traveled in the direction opposite to the negatively charged cathode rays, it seemed that they must be composed of positively charged particles. Rutherford suggested that this fundamental positive particle be called the proton.