CHEMISTRY GLOSSARY

hydrophobic interaction    →   hidrofobne interakcije

Hydrophobic interaction is the tendency of hydrocarbons (or of lipophilic hydrocarbon-like groups in solutes) to form intermolecular aggregates in an aqueous medium, and analogous intramolecular interactions. The name arises from the attribution of the phenomenon to the apparent repulsion between water and hydrocarbons. Use of the misleading alternative term hydrophobic bond is discouraged.

ionisation    →   ionizacija

Ionisation is the process of producing ions. Certain molecules ionise in a solution; for example, acids ionise when dissolved in water.

Electron transfer also causes ionisation in certain reactions, for example sodium and chlorine react by transfer of a valence electron from the sodium atom to the chlorine atom to form the ions that constitute a sodium chloride crystal.

ketone    →   keton

Ketones are compounds in which a carbonyl group is bonded to two carbon atoms: R₁R₂C=O (neither R may be H). They are derived by oxidation of secondary alcohols. The simplest member of the series is acetone, (CH₃)₂CO.

Lewis structure    →   Lewisova struktura

Lewis structure is the representation of the electron arrangement in atoms, ions, or molecules by showing the valence electrons as dots placed around the symbols for the elements.

ligand    →   ligand

Ligand is an ion (F^-, Cl^-, Br^-, I^-, S^2-, CN^-, NCS^-, OH^-, NH₂^-) or molecule (NH₃, H₂O, NO, CO) that donates a pair of electrons to a metal atom or ion in forming a coordination complex. The main way of classifying ligands is by the number of points at which they are attached to, or bound to, the metal center. This is the denticity. Ligands with one potential donor atom are monodentate. Polydentate ligand is a ligand that is attached to a central metal ion by bonds from two or more donor atoms. Ligands with more than one potential donor atom are known as ambidentate, such as the thiocyanate ion, NCS-, which can bind to the metal center with either the nitrogen or sulphur atoms. Chelating ligands are those polydentate ligands which can form a ring including the metal atom.

mass-energy equivalence    →   ekvivalencija mase i energije

In the special theory of relativity Einstein demonstrated that neither mass nor energy were conserved separately, but that they could be traded one for the other and only the total "mass-energy" was conserved. The relationship between the mass and the energy is contained in what is probably the most famous equation in science,

Where m is the mass of the object and c is the velocity of light. Cockcroft and Walton (1932) are routinely credited with the first experimental verification of mass-energy equivalence.

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.

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.

Newman’s projection    →   Newmanova projekcija

Newman’s projection is an image which we get when we observe a model of ethane molecule in C-C bond direction.

nonpolar molecule    →   nepolarna molekula

Nonpolar molecule is a molecule which has no separation of charge, so no positive or negative poles are formed. For example, the Cl₂ molecule has no polar bonds (molecule with one type of atom), CH₄ is a non-polar molecule (due to its symmetry). Nonpolar molecules do not dissolve in water as they cannot form hydrogen bonds (thus are hydrophobic) but do dissolve in lipids or fats (lipophilic).