CHEMISTRY GLOSSARY

metre    →   metar

Metre (m) is the SI base unit of length.

The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 s.

This definition, adopted by the General Conference on Weights and Measure in October 1983, replaced the 1967 definition based on the krypton lamp.

microscope    →   mikroskop

Microscope is an instrument that produces enlarged images of small objects. The optical microscopes (light microscope) use visible light and a system of lenses to magnify images. Typical magnification of a light microscope is up to 1500× ("1500 times")with a theoretical resolution limit of around 200 nm. Instead of using light, electron microscopes transmit a beam of electrons through, or onto the surface of, a specimen. An electron beam has a much shorter wavelength than does light, and can reveal structures as small as 2 nm.

Moh’s scale    →   Mohsova skala

Mohs’ scale of mineral hardness characterises the scratch resistance of various minerals through the ability of a harder material to scratch a softer. It was created by the German mineralogist Friedrich Mohs (1773-1839). Mohs based the scale on the ten readily available minerals.

mole    →   mol

Mole (mol) is the SI base unit of amount of substance.

The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of carbon 12.

When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles. In this definition, it is understood that the carbon 12 atoms are unbound, at rest and in their ground state.

molecular shape    →   oblik molekule

Molecular shape is the three dimensional arrangement of atoms in space around a central atom. The molecular formula of a substance does not give an indication of its shape. For example, CO₂ is a linear molecule, but SO₂ is angular.

The three-dimensional shapes of many small molecules can be predicted by applying the valence shell electron pair repulsion theory (VSEPR). When atoms combine to form molecules, pairs of valence electrons arrange themselves as far from each other as possible. Another way to characterize molecular shape is in terms of hybrid orbitals.

nickel    →   nikal

Nickel was discovered by Axel Fredrik Cronstedt (Sweden) in 1751. The origin of the name comes from the German word kupfernickel meaning Devil’s copper or St Nicholas’s (Old Nick’s) copper. It is hard, malleable, silvery-white metal. Soluble in acids, resist alkalis. It can be polished to a lustrous finish. Resists corrosion in air under normal conditions. Nickel is chiefly found in pentlandite [(Ni,Fe)₉S₈] ore. The metal is produced by heating the ore in a blast furnace which replaces the sulfur with oxygen. The oxides are then treated with an acid that reacts with the iron not the nickel. Used in electroplating and metal alloys because of its resistance to corrosion. Also in nickel-cadmium batteries, as a catalyst and for coins.

nitrogen    →   dušik

Nitrogen was discovered by Daniel Rutherford (Scotland) in 1772. The origin of the name comes from the Greek words nitron genes meaning nitre and forming and the Latin word nitrum (nitre is a common name for potassium nitrate, KNO₃). It is colourless, odourless, generally inert gas. Minimally reactive at room temperature. A component of many organic and inorganic compounds. Makes up about 78 % of earth’s atmosphere. Nitrogen is obtained from liquid air by fractional distillation. Primarily to produce ammonia and other fertilizers. Also used in making nitric acid, which is used in explosives. Also used in welding and enhanced oil recovery.

non-metal    →   nemetal

Non-metals are defined as elements that are not metals.

Their physical properties generally include:

• They are poor conductors.
• They are brittle, not ductile in their solid state.
• They show no metallic lustre.
• They may be transparent or translucent.
• They have low density.
• They form molecules which consists of atoms covalently bonded; the noble gases are monoatomic.

Their chemical properties are generally:

• They usually have four to eight valence electrons.
• They have high electron affinities (except the noble gases)
• They are good oxidising agents (except the noble gases)
• They have hydroxides which are acidic (except the noble gases)
• They are electronegative.

nuclear magnetic resonance    →   nuklearna magnetska rezonancija

Nuclear magnetic resonance (NMR) is a type of radio-frequency spectroscopy based on the magnetic field generated by the spinning of electrically charged atomic nuclei. This nuclear magnetic field is caused to interact with a very large (1 T - 5 T) magnetic field of the instrument magnet. NMR techniques have been applied to studies of electron densities and chemical bonding and have become a fundamental research tool for structure determinations in organic chemistry.

octet rule    →   pravilo okteta

Octet rule states that the chemical properties of the elements repeat on a regular basis with increasing atomic mass, and that the chemical properties of each eight element are similar. Since the inert gases, with the exception of helium have eight electrons in their outer shells, this stable electronic configuration is called the octet rule. In chemical reactions atoms of elements tend to react in such a way as to achieve the electronic configuration of the inert gas nearest to them in the periodic table. There are a number of exceptions to the octet rule.