Bonding in Metals
Objectives Be able to model the valence
electrons of metal atoms Describe the arrangement of
atoms in a metal Explain the importance of
alloys
Important Vocabulary
Metallic bondsAlloys
Metals Metals are made up of closely packed
cations rather than neutral atoms The valence electrons of metal
atoms can be modeled as a sea of electrons
Valence electrons move freely between metal atoms
Metallic Bond Is a bond formed by the attraction
between positively charged metal ions & the electrons around them
Attractive forces between nuclei and neighboring atom’s electrons pack the atoms close together, overlapping the energy levels creating the sea-of-electrons model
Metallic Properties Metallic properties can be explained
by the sea-of electrons model How? They are malleable and ductile Malleable means that they are
easily formed Ductile means that they can be
drawn into wires
Sea-of-Electrons
Crystalline Structure of Metals
Metals are crystalline Metals that contain just one kind of
atom are among the simplest forms of all crystalline solids
Metal atoms are arranged in very compact and orderly patterns
3 main arrangements: body-centered cubic, face-centered cubic, and hexagonal close-packed
Body-Centered Cubic Structure
Every atom (except those on the surface) has eight neighbors
Examples: sodium, potassium, iron, chromium, & tungsten
Face-Centered Cubic Structure
Every atom has 12 neighbors
Examples: copper, silver, gold, aluminum, and lead
Hexagonal Close-Packed Structure
Every atom has 12 neighbors
Examples: magnesium, zinc & cadmium
Alloys Are mixtures composed of 2 or
more elements, in which at least one is a metal
Why are alloys important?
Sterling Silver Sterling silver is a mixture of
7.5% copper & 92.5% silver It is harder and more durable than
pure silver but soft enough to made into jewelry and tableware
Bronze Is an alloy generally
containing 7 parts of copper to 1 part of tin
It is harder than copper and more easily cast
Nonferrous (non-iron) alloys such as, bronze, copper-nickel and aluminum alloys are commonly used to make coins
Steels Are the most important alloys The principal elements in most steels are
iron, carbon, boron, chromium, manganese, molybdenum, nickel, tungsten, and vanadium
Steels have a wide range of useful properties such as, corrosion resistance, ductility, hardness, & toughness
Steels are interstitial alloys, the smaller atoms can fit into the interstices (spaces) between the larger atoms
Steels