CHEMISTRY GLOSSARY

nascent state    →   nascentno stanje

Nascent state is an especially active state of an element in a moment when it is released from a compound during chemical reaction, e.g. nascent hydrogen.

nomenclature    →   nomenklatura

Nomenclature is a system of naming elements, ions and compounds.

Pauling scale    →   Paulingova skala

Pauling scale is a numerical scale of electronegativities based on bond-energy calculations for different elements joined by covalent bonds. Electronegativity is the power of an atom when in a molecule to attract eletrons to itself. Fluorine is the most electronegative element with a Pauling electronegativity value of 4.

manganese    →   mangan

Manganese was discovered by Johann Gahn (Sweden) in 1774. The origin of the name comes from the Latin word magnes meaning magnet, or magnesia nigri meaning black magnesia (MnO₂). It is hard, brittle, grey-white metal with a pinkish tinge. Impure forms are reactive. Rusts like iron in moist air. Manganese is most abundant ores are pyrolusite (MnO₂), psilomelane [(Ba,H₂O)₂Mn₅O₁₀] and rhodochrosite (MnCO₃). Pure metal produced by mixing MnO₂ with powered Al and ignited in a furnace. Used in steel, batteries and ceramics. The steel in railroad tracks can contain as much as 1.2 % manganese. It is crucial to the effectiveness of vitamin B₁.

metal    →   metal

Metals are materials in which the highest occupied energy band (conduction band) is only partially filled with electrons.

Their physical properties generally include:

- They are good conductors of heat and electricity. The electrical conductivity of metals generally decreases with temperature.

- They are malleable and ductile in their solid state.

- They show metallic lustre.

- They are opaque.

- They have high density.

- They are solids (except mercury)

- They have a crystal structure in which each atom is surrounded by eight to twelve near neighbours

Their chemical properties generally are:

- They have one to four valence electrons.

- They have low ionisation potentials; they readily lose electrons.

- They are good reducing agents.

- They have hydroxides which are bases or amphoteric.

- They are electropositive.

Metallic characteristics of the elements decrease and non-metallic characteristics increase with the increase of valence electrons. Also metallic characteristics increase with the number of electron shells. Therefore, there is no sharp dividing line between the metals and non-metals.

Of the 114 elements now known, only 17 show primarily non-metallic characteristics, 7 others are metalloids, and 89 may be classed as metals.

noble gas    →   plemeniti plin

Noble gas refers to any element of the group of six elements in group 18 of the periodic table. They are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). Unlike most elements, the noble gases are monoatomic. The atoms have stable configurations of electrons. Therefore, under normal conditions they do not form compounds with other elements.

They were generally called inert gases until about 1962 when xenon tetrafluoride, XeF₄, was produced in the laboratory. This was the first report of a stable compound of a noble gas with another single element.

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.

relative atomic mass    →   relativna atomska masa

Relative atomic mass (A_r) is the ratio of the average mass per atom of the naturally occurring form of an element to 1/12 of the mass of nuclide ¹²C. The term atomic weight is synonymous with the relative atomic mass.

short periods    →   kratke periode

Short periods are the second and third period of Periodic table of the elements. They are called short because there are only eight elements in each.

Newton’s gravitational law    →   Newtonov zakon gravitacije

Every object in the universe attracts every other object with a force (gravitational force F_G) directed along the line through centres of the two objects that is proportional to the product of their masses and inversely proportional to the square of the distance between them.

m₁ and m₂ are masses of the two objects and r is the distance between them. G is universal constant of gravitation, which equals 6.67•10^-26 N m² kg^-2. Strictly speaking, this law applies only to objects that can be considered pointlike object. Otherwise, the force has to be found by integrating the forces between various mass elements.

It is more properly to express Newton’s gravitational law by vector equation:

in which r₁ and r₂ are position vectors of masses m₁ and m₂.

Gravitational forces act on distance. Newton’s gravitational law is derived from Kepler’s law for planetary motion, using a physical assumption considering Sun as the centre and the source of gravitational force.

Additionally, every object moves in the direction of the force acting on it, with acceleration that is inversely proportional to the mass of object. For bodies on the surface of Earth, the distance r in gravitational law formula is practically equal to the Earth radius, R_E. If the mass of the body on Earth surface is m and the mass of earth is M_E, the gravitational force acting on that body can be expressed as:

where g is gravitational acceleration which is, although dependent on geographical latitude, usually considered as constant equal to 9.81 m s^-2.