CHEMISTRY GLOSSARY

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.

starch    →   škrob

Starch (C₆H₁₀O5)_x is a polysaccharide used by plants to stockpile glucose molecules. It is the major component of flour, potatoes, rice, beans, corn, and peas. Starch is a mixture of two different polysaccharides: amylose (about 20 %), which is insoluble in cold water, and amylopectin (about 80 %), which is soluble in cold water. Amylose is composed of unbranched chains of D-glucose units joined by α(1→4)-glycosidic linkages. Unlike amylose, which are linear polymers, amylopectin contains α(1→6)-glycoside branches approximately every 25 glucose units.

Starch digestion begins in the mouth via the action of amylase, a digestive enzyme present in saliva. The process is completed in the small intestine by the pancreatic amylase. The final products of starch digestion, glucose molecules, are absorbed into the intestinal bloodstream and transported to the liver. Like most enzymes, glycosidases are highly selective in their action. They hydrolyze only the α-glycoside links in starch and leave the β-glycoside links in cellulose untouched. Starch is important food stuff and is used in adhesives, and sizes, in laundering, pharmacy and medicine.

structural formula    →   strukturna formula

Structural formula is a two dimensional representations of the arrangement of the atoms in molecules. Atoms are represented by their element symbols and covalent bonds are represented by lines. The symbol for carbon is often not drawn.

sucrose    →   saharoza

Sucrose (saccharose), or ordinary table sugar, is a disaccharide in which α-D-glucopyranose and β-D-fructofuranose are joined at their anomeric carbons by a glycosidic bond. There are no hemiacetals remaining in the sucrose and therefore sucrose is not a reducing sugar and does not exhibit mutarotation. Sugar is a white crystalline sweet compound found in many plants and extracted from sugar cane and sugar beet. It is used as a sweetening agent in food and drinks. If heated to 200 °C, sucrose becomes caramel. When sucrose is hydrolyzed it forms an equimolar mixture of glucose and fructose. This mixture of monosaccharides is called invert sugar. Honeybees have enzymes called invertases that catalyze the hydrolysis of sucrose. Honey, in fact, is primarily a mixture of glucose, fructose, and sucrose.

T-shaped molecular geometry    →   T-oblik geometrije molekule

T-shape is a molecular geometry that results when there are 3 bonds and 2 lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the ends of a T with 90° angles between them. Molecules with an trigonal bipyramidal electron pair geometries have sp³d (or dsp³) hybridization at the central atom. ICl₃ has a T-shaped molecular geometry.

tetrahedral molecular geometry    →   tetraedarska geometrija molekule

Tetrahedral is a molecular shape that results when there are four bonds and no lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the corners of a tetrahedron with 109.5° angles between them. Molecules with an tetrahedral electron pair geometries have sp³ hybridization at the central atom. The ammonium ion (NH₄⁺) and methane (CH₄) have a tetrahedral molecular geometry.

trigonal bipyramidal molecular geometry    →   trigonska bipiramidalna geometrija molekule

Trigonal bipyramidal (trigonal bipyramidal shape) is a molecular geometry that results when there are five bonds and no lone pairs on the central atom in the molecule. Three of the bonds are arranged along the atom’s equator, with 120° angles between them; the other two are placed at the atom’s axis. Axial bonds are at right angles to the equatorial bonds. Molecules with an trigonal bipyramidal electron pair geometries have sp³d (or dsp³) hybridization at the central atom. The PCl₅ molecule has a trigonal bipyramidal molecular geometry.

trigonal planar molecular geometry    →   trigonska planarna geometrija molekule

Trigonal planar is a molecular shape that results when there are three bonds and no lone pairs around the central atom in the molecule. The pairs are arranged along the central atom’s equator, with 120° angles between them. Molecules with an trigonal planar electron pair geometries have sp²d hybridization at the central atom. The carbonate ion (CO₃^2-) has a trigonal planar geometry.

trigonal pyramidal molecular geometry    →   trigonska piramidalna geometrija molekule

Trigonal pyramidal is a molecular shape that results when there are three bonds and one lone pair on the central atom in the molecule. Molecules with an tetrahedral electron pair geometries have sp³ hybridization at the central atom. Ammonia (NH₃) is a trigonal pyramidal molecule.