bonding in metals. objectives be able to model the valence electrons of metal atoms describe the...

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