Chemistry Second 9 weeks 3

Review Ionic covalent--and-metallic- bonds?playlist=Chemistry covalent--and-metallic- bonds?playlist=Chemistry 0 to 6:11 is ionic compound review ntroduction/bonding.introduction.html ntroduction/bonding.introduction.html

Class Today Metallic Bonding

Metallic Bonds and Properties of Metals Metals form crystal lattices and can be modeled as cations surrounded by a “sea” of freely moving valence electrons.

Elemental Metal Samples Metals exist as cations surrounded by a sea of electrons. It is not ionic although they share some of the same properties as ionic compounds. The metal ions bond based on the attraction of particles of unlike charges and Metals form lattices in the solid states similar to ionic crystal lattices.

A Sea of Electrons Metals will always have at least one velence electron. They do not share these with the neighboring atoms. They do not lose their valence electron. INSTEAD..with the crowded lattice, the outer energy levels of the metal atoms overlap so that the metal atoms contribute their valence electron to form a “sea” of electrons.

A Sea of Electrons This sea of electrons surrounds the metal cations in the lattice The metal ions are so close that the electrons in the outer energy levels are not held by a specific atom but can move easily from one atom to the next. These electrons are “delocalized electrons” Each metal ion is bonded to the other metal ion by the sea of valence electrons.

Metallic Bond Attraction of a metallic cation for the delocalized electrons. See picture on textbook page 225

Properties of Metals Are explained by the metallic bonding and sea of electrons The melting point of metals vary greatly. Mercury is liquid at room temperature. Tungsten has a mp of 3422 degrees Celsius. (6192 degrees Fahrenheit)

Properties of Metals Metals are malleable (can be hammered into sheets) Ductile (drawn in to wires) Durable generally Movement of mobile electrons makes metals good conductors. The delocalized electrons move heat from one place to another much more quickly than electrons in a material without mobile electrons.

Properties of Metals The same delocalized electrons interact with light, absorbing and releasing photons, thereby creating the property of luster in metals. The mobile electrons in transition metals include both the 2 outer s electrons as well as the inner d electrons. As the # of delocalized electrons increases, so do the properties of hardness and strength.

Properties of Metals Strong metallic bonds are found in chromium, iron and nickel, whereas the alkali metals are soft because they have only one delocalized electron (ns 1 ). Metal alloys: mixture of elements that has metallic properties. Alloys have a wide range of applications: stainless steel, brass, cast iron, pewter, bronze.