Contributed by:
The highlights are:
1. Metallic bonds
2. Properties of metals
3. Alloys
2.
What are Metals?
A metal is an element that readily forms
positive ions (cations) and has metallic
3.
What are Metals?
On the periodic table, a diagonal or stair step line
drawn from boron (B) to polonium (Po) separates the
metals from the nonmetals. Elements on this line are
metalloids, sometimes called semi-metals; elements
to the lower left are metals; elements to the upper
right are nonmetals.
Almost 80% of the elements on the periodic table are
4.
Metallic Bonds
The valence electrons of metal atoms can
drift freely from one part of the metal to
another- this is sometimes
called a “sea of electrons”
Metallic bonds consist of
the attraction between these
free floating electrons and the
positively charged metal ions (cations).
This attraction is the “bond” that holds
metals together.
5.
Physical Properties of Metals
Lusterous- they are shiny!
High density- atoms are tightly packed.
Good conductors of electricity and heat.
Reason- electrons can flow freely.
6.
Physical Properties of Metals
Ductile- they can be drawn into wires AND
Malleable- they can be hammered into
Reason- cations can slide easily past each
other because the sea of electrons insulates
them and prevents strong repulsions.
7.
…on the other hand
Ionic compounds are brittle and break
easily? Why
8.
Physical Properties of Metals
Metal ions are arranged in very compact
orderly patterns.
–Similar to the way apples are stacked at
the grocery store.
Pure metals form the simplest kinds of
9.
Chemical Properties of Metals
Most metals are chemically unstable and
will react will oxygen in the air- that is they
form oxides- over varying timescales (for
example iron
rusts over years
and potassium
burns in seconds).
10.
Chemical Properties of Metals
-The alkali metals react quickest followed by the
alkaline earth metals.
-The transition metals take much longer to oxidize
(such as iron, copper, zinc, nickel). Others, like
palladium, platinum and gold, do not react with
the atmosphere at all.
-Some metals form a barrier layer of oxide on their
surface which cannot be penetrated by further
oxygen molecules and thus retain their shiny
appearance and good conductivity for many
decades (like aluminium, some steels, and
titanium).
11.
Alloys
Very few metals that you encounter daily are pure
metals. Most metals are alloys, a mixture of two or
more elements of which at least one is a metal.
Examples:
Brass is an alloy of copper and zinc
Sterling silver is an alloy of silver (92%) and copper (8%)
Stainless Steel is an alloy of iron (81%), chromium (18%), nickel
(1%), and trace amounts of carbon.
Alloys are important because their properties are
often superior to those of their component elements.
Examples:
Sterling silver is harder and more durable than pure silver, but still
soft enough to make jewelry and tableware.
Brass is harder and easier to shape than either copper or zinc
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