Metallic Bonding PDF

Chemical bonding The metallic bond Bonding between metal atoms Properties of metals Alloys Metallic bond Bonding between metal atoms There are a number of reasons to believe that there are types of bonds other than ionic bonds and covalent bonds. A positive and negative cha...

Chemical bonding The metallic bond Bonding between metal atoms Properties of metals Alloys Metallic bond Bonding between metal atoms There are a number of reasons to believe that there are types of bonds other than ionic bonds and covalent bonds. A positive and negative charge for identical atoms in single substances are difficult to imagine. Metal atoms have too few valence electrons to achieve noble gas configuration. Metallic bond Bonding between metal atoms Metals at atomic level: Metal atoms give their valence electrons away. These will be detached from the metal atoms and form a sea of delocalized electrons in which the positively charged metal atoms swim. Model: Metallic bond: Strong electrostatic attraction between the positively charged metallic ions and the sea of negatively charged delocalized electrons Metallic bond Examples Metallic bond Properties of metals Metals have some unique properties: Metallic shine Examples: tin silver gold lithium mercury Colour: metals have a grey colour. Gold and Copper form exceptions Physical state at rtp: metals are solid. Mercury forms an exception Metallic bond Properties of metals Metals have some unique properties: Good conductivity of heat and electricity Useful for cooking Copper in electric wires Metallic bond Properties of metals Metals have some unique properties: High melting point, great hardness and high density Tungsten (W) has the highest melting Small weights with a big point (3410°C) mass Osmium: 1 liter has a mass of 22.59 kg!!!  Metallic bond Properties of metals Metals have some unique properties: Malleability (stretchable, cuttable and foldable) vs Brittleness of salts METALS SALTS Ionic lattice is disrupted Metallic lattice is NOT disrupted Same charges get into → Salts are malleable contact and cause a rupture → Salts are brittle Metallic bond Properties of metals Metals have some unique properties: Malleability (stretchable, cuttable and foldable) rolling of aluminium Sodium can be cut Watertight with a knife through lead around window frames (formerly used) Metallic bond Alloys Metallic bond Alloys A MIXTURE of one metal with another metal or non-metal is an alloy. There are a number of types of alloys. Replacing atoms with atoms of similar atomic radius. → Creating "solid solution" with new properties. Example: brass (copper with zinc, ex. 10, 20 and 50 cts € coins) bronze (copper with tin) Stainless steel (carbon (NM!), chromium and nickel) Atoms replaced by atoms with much smaller atomic radius. → Prevents metal lattice disruption Example: hard steel (steel with carbon) Metallic bond Practice Metallic bond Practice