CHEMISTRY GLOSSARY

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.

radiography    →   radiografija

Radiography is nondestructive method of internal examination in which metal objects are exposed to a beam of X-ray or gamma radiation. Differences in thickness, density, or absorption caused by internal defects or inclusions are apparent in the shadow image produced on a fluorescent screen or photographic film placed behind the object.

Raman effect    →   Ramanov efekt

Raman effect is a type of scattering of electromagnetic radiation in which light suffers a change in frequency and a change in phase as it passes through a material medium. Named according to the Indian physicist C. V. Raman (1889-1970). The intensity of Raman scattering is about one-thousandth of that in Rayleigh scattering in liquids.

Rankine cycle    →   Rankineov ciklus

Rankine cycle is a thermodynamic cycle which can be used to calculate the ideal performance of a heat engine that uses a condensable vapour as the working fluid.

Raoult’s law    →   Raoultov zakon

Raoult’s law is the expression for the vapour pressure p_A of component A in an ideal solution, viz.,

where x_A is the mole fraction of component A and p_A^o the vapour pressure of the pure substance A.

Kohlrausch’s law    →   Kohlrauschov zakon

Kohlrausch’s law states that the equivalent conductivity of an electrolyte at infinite dilution is equal to the sum of the conductances of the anions and cations. If a salt is dissolved in water, the conductivity of the solution is the sum of the conductances of the anions and cations. The law, which depends on the independent migration of ions, was deduced experimentally by the German chemist Friedrich Kohlrausch (1840-1910).

lanthanides    →   lantanoidi

Lanthanides (lanthanons, lanthanoids or rare-earth elements) are a series of fourteen elements in the periodic table, generally considered to range in proton number from cerium to lutetium inclusive. It was convenient to divide these elements into the cerium group or light earth: cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu); and the yttrium group or heavy earths: gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) i lutetium (Lu). The position of lanthanum is somewhat equivocal and, although not itself a lanthanide, it is often included with them for comparative purpose. The lanthanides are sometimes simply called the rare earths. Apart from unstable Pm, the lanthanides are actually not rare. Cerium is the 26. most abundant of all elements, 5 times as abundant as Pb. All are silvery very reactive metals.

reactivity    →   reaktivnost

Reactivity is the tendency of a compound to chemically react with other substances or itself, resulting in the release of energy.

reactivity series    →   reaktivni niz

Reactivity series or activity series is a series of elements (usually metals) ranked by their reactivity degree, made for comparison of reactions of elements with other substances, e.g. acids and oxygen.

law of conservation of mass    →   zakon o očuvanju mase

Law of conservation of mass states that no detectable gain or loss in mass occurs in chemical reactions. The state of a substance may change in a chemical reaction, for example, from a solid to a gas, but its total mass will not change. Note that the energy released (exothermic) or adsorbed (endothermic) in a chemical reaction is a result of energy transfer between atoms and their environment.