Introduction: To gain a better insight of the molecular structures of these materials, we must understand general types of bonding (primary and secondary) that will further explain their properties. A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. Because this bond involves the sharing of electrons, giving each atom the opportunity to fill their outer orbital shell (octet rule), it provide a stable electron configuration. They are usually formed between two nonmetal elements for they have similar electronegativity. Covalent bonds have several properties: they are involved in gases, liquids, or solids, have low melting and boiling points, and are poor electrical conductors . An ionic bond is the result of electron transfer from one atom to another. They are formed through electrostatic attractions between a metal cation (positive) and a non-metal anion (negative). Contrast to covalent bonds, these bonds are non-directional. Properties of ionic bonds: high melting and boiling points, conduct electricity when melted, and brittle. Metallic bonds involves electron sharing, and is nondirectional. Valance electrons within these bonds are delocalized, giving the freedom to move freely as a ‘sea of electrons’ surrounding cation metals. Because of this, the delocalized electrons proved high electrical conductivity . Metal bonds are tightly packed, having high coordination numbers, which explains why it’s malleable, ductile, and high melting and boiling points. Van der Waals bonding, classified as a secondary bond due to weak attractive forces, are dipole where they are either permanent or temporary bonds (London dispersion) . These bond are involve in polymers where we used during lab. The purpose of this experiment is to conclude why such materials behave this way and their properties by collecting measurements such as volume, weight, density, conductivity, and hardness. After understanding the concept of primary and secondary bonds, we expect metals to have a larger weight, density, and hardness, and having the ability to conduct electricity. In contrast, polymers will lack properties that metals inhibit and conclude that they are poor conductors of electricity.
For this lab, we measured the weight, volume, electrical conductivity, and hardness of the following materials: brass, copper, steel, aluminum, polycarbonate, polyethylene, and polystyrene. Weight was simply measured on a scale to the nearest .01g. Volume was calculated in two ways: (1) submerging the material in a graduated cylinder filled with water and measuring the displacement (the difference between the elevated height of water by submerged material and original height of water), (2) measuring the length, width, and thickness of the material with the use of the caliper, calculating volume by drawing shapes, relative to the shape of the material like rectangles, triangles, and squares(once again, lack of the time