A metal is a kind of matter, usually derived from rocks found in nature. Examples of metals include iron, aluminum, and brass. Atomic structure, discussed later in this article, creates the distinct properties of metals.
Properties of Metal
Gold nugget–gold as the metal is sometimes found in nature (if you’re lucky!) [Image source: http://resourcescommittee.house.gov/subcommittees/emr/ usgsweb/photogallery/, Public Domain, https://commons.wikimedia.org/w/index.php?curid=38780, Retrieved from https://en.wikipedia.org/wiki/Metal July 8, 2017]Metals are:
Hard
Opaque
Shiny
Meltable
Malleable, that is, they hold together when beaten or rolled into various shapes
Ductile, that is, they can be drawn into thin threads
Good conductors of heat
Good conductors of electricity
In the case of some metals, magnetizable
Atomic Structure of Metals
The properties of metals result from their unique atomic structure. Most metals are formed by a “lattice” of atoms. A lattice is an arrangement of atoms in a regular pattern resulting in the formation of crystals.*
Metal ions in a sea of electrons. [Image source: Jkwchui – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=12617370 Retrieved from https://en.wikipedia.org/wiki/Ion July 6, 2017] This diagram shows the atomic arrangement of metals. Atoms are shown in blue with a central black nucleus. Electrons which originate in the outermost part of the atom flow loosely about the lattice. That is, they fly out of their atoms and form a jittering sea of electrons not bonded with any particular atom. So, the blue atoms are more accurately called “ions” and have a positive charge. The loose electrons are called “free electrons” or “conductivity electrons.” They are responsible for the good heat and electrical conductivity of metals. They also play a key role in magnetism.
Gold atoms on the surface of a crystal of gold. Each atom appears as a little spherical cell. The atoms at the surface arrange themselves in columns, shown as diagonals. Each column is several atoms across. Dark channels form between the columns. This image was created by a high-powered microscope (a scanning tunneling microscope). [Image source: Public Domain, https://commons.wikimedia.org/wiki/File:Atomic_resolution_Au100.JPG Retrieved June 17, 2017]The lattice arrangement of ions in metals creates the regularity visible when metals are viewed through powerful microscopes. As noted, while it is common to describe the little spheres in the accompanying image of gold as “atoms,” they are more specifically, “ions.” The lattice structure also creates the regularity apparent in crystals of metal (see image of gold above).
Some metals, usually alloys, are not formed in a lattice, crystalline structure, but rather take an “amorphous” form. The details of the amorphous atomic structure are not covered in this article.
Metallic Bonding
The type of lattice structure described above is formed by metallic bonding. The ions, each positively charged, would ordinarily repel each other. However, the sharing of free electrons holds the ions together. Metallic bonding is one of three types of bonds that form aggregations of atoms. In the case of metallic bonding, the aggregations are usually crystals rather than molecules.
The other two types of bonds often, though not always, form molecules rather than crystals. They are ionic bonding and covalent bonding.
Metals in the Periodic Table of Elements
Most of the elements in the Periodic Table of Elements are metals.
The Periodic Table of Elements. Elements shown in yellow are metals in ordinary conditions of temperature, pressure, etc. Elements shown in blue are nonmetals. Elements shown in khaki are metalloids, which have both metallic and nonmetallic properties. [Image source: Retrieved from https://en.wikipedia.org/wiki/Metal July 8, 2017.]*What we perceive as a lattice at the atomic scale (microscopic scale), we perceive as crystals at the everyday scale of tables and chairs (macroscopic scale).
