CHEMISTRY GLOSSARY

sp hybrid orbital    →   sp hibridna orbitala

An sp hybrid orbital is an orbital formed by the linear combination of one s and one p orbital of comparable energy (such 2s and 2p orbitals) on a same atom. The two sp hybrid orbitals are aligned in a straight line in opposite direction (bond angles are 180°). The remaining two p orbitals are at right angles to one another and to the line formed by the two sp orbitals.

sp2 hybrid orbital    →   sp2 hibridna orbitala

An sp² hybrid orbital is an orbital formed by the linear combination of one s and two p orbitals of comparable energy (such 2s and 2p orbitals) on a same atom. The three sp² hybrid orbitals lie in a plane with angle of 120°. The remaining p orbital remains unchanged and is perpendicular to the plane of the three sp² orbitals.

sp3 hybrid orbital    →   sp3 hibridna orbitala

An sp³ hybrid orbital is an orbital formed by the linear combination of one s and three p orbitals of comparable energy (such 2s and 2p orbitals) on a same atom. The four sp³ hybrid orbitals point toward the corners of a regular tetrahedron with the bond angle of 109.5°.

spectrophotometer    →   spektrofotometar

Spectrophotometer is an instrument for measuring the amount of light absorbed by a sample.

The absorption of light by a substance in a solution can be described mathematically by the Beer-Lambert law

where A is the absorbance at a given wavelength of light, ε is the molar absorbtivity or extinction coefficient (L mol^-1 cm^-1), unique to each molecule and varying with wavelength, b is the length of light path through the sample (cm), and c is the concentration of the compound in solution (mol L^-1).

spin    →   spin

Spin is the intrinsic angular momentum of an elementary particle, or system of particles such as nucleus, that is also responsible for the magnetic moment; or, a particle or nucleus possessing such a spin. The spins of nuclei have characteristic fixed values. Pairs of neutrons and protons align to cancel out their spins, so that nuclei with an odd number of neutrons and/or protons will have a net non-zero rotational component characterized by a non-zero quantum nuclear spin number.

Stern-Gerlach experiment: a beam of silver atoms is split into two beams when it traverses a nonuniform magnetic field. Atoms with spin quantum number m_s=+1/2 follow one trajectory, and those with m_s=+1/2 follow another.

square planar molecular geometry    →   kvadratna planarna geometrija molekule

Square planar is a molecular shape that results when there are four bonds and two lone pairs on the central atom in the molecule. An example of a square planar molecule is xenon tetrafluoride (XeF₄). This molecule is made up of six equally spaced sp³d² (or d²sp³) hybrid orbitals arranged at 90° angles. The shape of the orbitals is octahedral. Two orbitals contain lone pairs of electrons on opposite sides of the central atom. The remaining four atoms connected to the central atom give the molecule a square planar shape.

square pyramidal molecular geometry    →   kvadratna piramidalna geometrija molekule

Square pyramidal is a molecular shape that results when there are five bonds and one lone pair on the central atom in the molecule. Bromine pentafluoride (BrF₅) has the geometry of a square pyramid, with fluorine atoms occupying five vertices, one of which is above the plane of the other four. This molecule is made up of six equally spaced sp³d² (or d²sp³) hybrid orbitals arranged at 90° angles. The shape of the orbitals is octahedral. Because of the high symmetry of the octahedral arrangement, all six positions are equivalent, so it does not matter in which position in the drawing we put the lone pair. The remaining four atoms connected to the central atom give the molecule a square planar shape.

standard deviation    →   standardna devijacija

Standard deviation (σ) is a measure of the dispersion of a set of data from its mean. Standard deviation is a statistical term that measures the amount of variability or dispersion around an average

Suppose there are many measurements of a quantity presumed to be similar, like the size of peas in a pod. If the number of readings for each size were plotted, a bell-shaped curve would probably result, with a few small and large peas and most clustered around the average size. Around two-thirds of all measurements fall in the range spanned by the standard deviation, a measure of the spread.

standard hydrogen electrode    →   standardna vodikova elektroda

Standard hydrogen electrode is a system in which hydrogen ion and gaseous hydrogen are present in their standard states. The convention is to designate the cell so that the standard hydrogen electrode is written first.

The electrode is used as a reference (of zero) for the values of other standard electrode potentials.

state of matter    →   agregatno stanje

State of matter is one of the tree physical states in which matter can exist, i.e. solid, liquid or gas. Plasma is sometimes regarded as the fourth state of matter. By means of heating a solid substance will cross to liquid state at its melting point. If we heat up a liquid and beyond, at its boiling point it will cross to gaseous state - vapour.