Two-dimensional 2D models Three-dimensional 3D models using

Proceeding of Chemistry Conferences vol. 1 2016 ISSN 2541-108X 46

3. Two-dimensional 2D models

In order to represent such configurations on a two-dimensional surface paper, blackboard or screen, we often use perspective drawings in which the direction of a bond is specified by the line connecting the bonded atoms. Figure 2 shows one of the examples of 2D perspective drawing of methane CH 4 in tetrahedral molecular geometry. The convention is that the central atom of carbon is placed in the plane of the surface paperblackboardscreen. Bonds to this atom which also lie in this plane are represented by a line of normal thickness, whereas bonds lying off this plane are represented differently. Bonds directed out in front of this plane are wedged, with an atomgroup at the thicker end of the wedge being interpreted as being nearer the viewer than the carbon to which the narrower end points. Bonds directed back behind this plane are hashedbroken . Two-dimensional 2D drawings inform us the positioning of atoms and bonds whether they are on the screen surface, behind it or in front of it. However, 2D drawing provides only a limited insight into the activity and molecular properties of a compound. These perspective structures have a limitation because it could not tell us the information about reasonably accurately the angles involved. Figure 2. Perspective drawing in two-dimensional 2D model of CH 4 in tetrahedral geometry

4. Three-dimensional 3D models using

Origami technique for exploring molecular geometry Aproper application such three-dimensional 3D configurations are the best way to get the more realistic perspective views. Three-dimensional 3D configurations can be viewed with the aid of models. Many 3D models for molecular geometry are available such as commercial molecular model kits, ball and stick models, software for molecular modeling, and computer simulation. However, many of commercial 3D models are expensive, while cheaper handmade model using plasticine, straw, toothpick or matchstick is easy to collapse relative fragility restrict. Another model such computer simulation has also a limitation for its simulation learning difficulties by students. Here we introduce one of the appropriate and simple 3D model, the origami technique for visualising the molecular shape method is a ‗hands-on‘ approach in building molecules expected more intention while gaining the building experiences. Origami , the art of paper folding, is often associated with the Japanese culture. The word of origami is taken from ori meaning folding and kami meaning paper. Technical Origami transforms a flat sheet square of paper folded into intricate designs. This technique not only supports in designing but also in other fields such as a study in the field of engineering, Proceeding of Chemistry Conferences vol. 1 2016 ISSN 2541-108X 47 mathematics, and science. In chemistry, origami might use as a model to approach the 3D molecular model. Flinn scientific already develop origami pattern for several geometries such as trigonal pyramidal, tetrahedral, seesaw, square pyramidal, trigonal bipyramidal and octahedral. Another source of origami kit also was provided by Hanson, 1995 in his book of Molecular Origami published by University Science Book. USA. The patterns are drawn in Figure 3 are taken from the later source. Figure 3. Origami patterns for trigonal-pyramidal and tetrahedral geometries. The patterns were drawn by solid and dashed lines. They are represented to ―mountain‖ folds, which fold away from the viewer and ―valley‖ folds, which fold toward the viewer. The shaded regions can be either removed or simply folded back and tucked into the hidden recesses of the model. The two basic 3D molecular shapes are trigonal-pyramidal and tetrahedral. The trigonal-pyramidal consists of four atoms with one central atom located above the plane of the other three atoms. The tetrahedral consists of five atoms, one central atom, and four surrounding atoms. An extra atom is situated above the other four atoms. Proceeding of Chemistry Conferences vol. 1 2016 ISSN 2541-108X 48

5. Applied cases: H