Polymers are plastics that are based on carbon Ceramics are combinations Metallic materials used group 1 and 2 on periodic table and transition and metal elements Following are semiconductors silicon diamond germanium cadmium selenide Cadmium selenium Melting points below carbon on the periodic table decrease as you get lower just a trend not always true 4 bonds metallic covalent iconic van der waals o First three are primary bond and relatively strong o Van der is secondary and a little weaker Metallic bond o Donate their valence electron to from a sea of electrons o Their valence electrons move freely within the electron sea means good conductors of electricity o Good ductility are non directional microstructure o Ductility ability to stretch or bend permanently without breaking melting points of metals are relatively high and good heat transfer applications o Metals are good reflectors of visible radiation Covalent bond Ionic bond o Sharing two or more atoms o Shares one covalent bond the covalent bonds are very strong o Cation anion o Opposite charged ions are attached to one another Ionic bond Van der Waals Bonding o They are separated by a distance o Atoms are electrically neutrals o The center of the nucleus and electron cloud conicide Binding energy energy required to create or break the bond Steeper slope higher binding energy and higher melting point which means a greater force is required to stretch the bond and then will have a high modulus of elasticity Diamond has the highest thermal conductivy which is due to the covalently bonded structure Diamond is the stiffest material with an elastic modulus of 1100 GPa Hardest substances As the material is head the atoms vibrate with more energy Diamond is really really important When you have valence electrons of each carbon there is no free electrons to conduct electricity