CHEMISTRY GLOSSARY
electron → elektron
The electron is an elementary particle with a negative electric charge of (1.602 189 2±0.000 004 6)×10-19 C and a mass of 1/1837 that of a proton, equivalent to (9.109 534±0.000 047)×10-31 kg.
In 1897 the British physicist Joseph John (J.J.) Thomson (1856-1940) discovered the electron in a series of experiments designed to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson interpreted the deflection of the rays by electrically charged plates and magnets as evidence of bodies much smaller than atoms that he calculated as having a very large value for the charge to mass ratio. Later he estimated the value of the charge itself.
Electrons are arranged in from one to seven shells around the nucleus; the maximum number of electrons in each shell is strictly limited by the laws of physics (2n2). The outer shells are not always filled: sodium has two electrons in the first shell (2×12 = 2), eight in the second (2×22 = 8), and only one in the third (2×32 = 18). A single electron in the outer shell may be attracted into an incomplete shell of another element, leaving the original atom with a net positive charge. Valence electrons are those that can be captured by or shared with another atom.
Electrons can be removed from the atoms by heat, light, electric energy, or bombardment with high-energy particles. Decaying radioactive nuclei spontaneously emit free electrons, called β particles.
electron microscope → elektronski mikroskop
Electron microscope is a form of microscope that uses a beam of electrons instead of a beam of light (as in the optical microscope) to form a large image of a very small object. In optical microscopes the resolution is limited by the wavelength of the light. High-energy electrons, however, can be associated with a considerably shorter wavelength than light; for example, electrons accelerated to energy of 105 electronvolts have a wavelength of 0.004 nm enabling a resolution of from 0.2 nm to 0.5 nm to be achieved.
monochromator → monokromator
Monochromator (from the Greek words mono and chroma meaning single and colour) is an optical device based on dispersion of light by one or more prisms or diffraction gratings into its constituent wavelengths, which are utilized in turn.refractive index → indeks loma
For a non-absorbing medium, refractive index (n) is the ratio of the velocity of electromagnetic radiation (light) in vacuum to the phase velocity of radiation of a specified frequency in the medium.
fructose → fruktoza
Fructose (fruit sugar) is a ketohexose (a six-carbon ketonic sugar), which occurs in sweet fruits and honey. Glucose and fructose have the same molecular formula, C6H12O6, but have different structures. Pure, dry fructose is a very sweet, white, odorless, crystalline solid. Fructose is one of the sweetest of all sugars and is combined with glucose to make sucrose, or common table sugar. An older common name for fructose is levulose, after its levorotatory property of rotating plane polarized light to the left (in contrast to glucose which is dextrorotatory). The polysaccharide inulin is a polymer of fructose.
global warming → globalno zatopljenje
Global warming or greenhouse effect is an effect occurring in the atmosphere because of the presence of certain gases (greenhouse gases) that absorb infrared radiation. Light and ultraviolet radiation from the sun is able to penetrate the atmosphere and warm the Earth’s surface. This energy is re-radiated as infrared radiation which because of its longer wavelength, is absorbed by such substances as carbon dioxide. The overall effect is that the average temperature of the Earth and its atmosphere is increasing (so-called global Warming). The effect is similar to that occurring in a greenhouse, where light and long-wavelength ultraviolet radiation can pass through the glass into greenhouse but the infrared radiation is absorbed by the glass and part of it is re-radiated into the greenhouse.
The greenhouse effect is seen as a major environmental hazard. Average increases in temperature could change weather patterns and agricultural output. It might also lead to melting of the polar ice caps and a corresponding rise in sea level. Carbon dioxide, from fossil-fuel power stations and car exhausts, is the main greenhouse gas. Other contributory pollutants are nitrogen oxides, ozone, methane, and chloroflourocarbons.
transmittance → transmitancija
Transmittance (τ) is the ratio of the radiant or luminous flux at a given wavelength that is transmitted to that of the incident radiation. Also called transmission factor.
Tyndall’s effect → Tyndallov efekt
Tyndall’s effect occurs when light disperses on colloid particles. This phenomenon can be seen when a ray of light enters in dark room through a small hole. In the beam some dust particles of colloid dimensions can be seen sparkling.
Citing this page:
Generalic, Eni. "Svjetlost." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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