Metals are an important component of everyday life. Metals are used in every electricat device we have, every appliance, every vehicle and every building we use. Man has used metal since 7000B.C.E.ca. Metals comprise a great majority of the periodic table and have their own type of bonding system and structure. Metals can be worked and hardened, shaped, and broken. Metals can be malleable, ductile, or brittle. Metals conduct heat and electricity. There are 86 known metals. Earth’s crust is 24.1% metal.
To fully understand metals one must start at the very fundamentals, their atomic structure, physical properties, and chemical properties, in short, chemistry. Chemically metals are defined as atoms being shiny and being good conductors, conductive of heat, and conductive of electricity. To the human eye metals are not individual atoms but a tightly metallic bonded group. Metallic bonds are formed from the electromagnetic interaction between delocalized electrons, called conduction electrons and gathered in an electron sea, which is the group of electrons in metal. Metallic bonds are the bonds between metals that share electrons in a community fashion due to their positive charge (lack of valence electrons). This strong metallic form of bondage makes for high melting and boiling points. Metals are dense matter due to their tightly packed structure in which as many atoms as can possibly fit are assembled together. As a result of the community sharing property of metallic bonds and their close proximity to each other electrons have quite free tri-dimensional movement capabilities, which allow for high conductibility of heat and electricity, which may be transferred in the same way. As long as atoms in a metallic bond are making contact electrons may be transferred, which does not exclude liquid metals such as Mercury (Hg).
Metals are generally formed in one of two structures, 12 and 8-coordinated. In 12-coordinated metallic structures each atom is surrounded by six atoms on each layer, 3 on the left, 3 on the right, and smashed between two layers. In 8-coordinated metallic structures there are four atoms on each layer, 2 on the left 2 on the right, and the atom is again smashed between two layers. This is the ideal structure of metals and is not always true as, due to the sharing rather than ridged, structure of metals they may be deformed and changed before breaking apart like more brittle substances, as a result of deformity there are frequent irregularities in a metals structure. This same aspect that allows for structural irregularities, this sliding of the atoms over each other, allows for malleability, capable of being shaped or bent, and ductility, capable of being drawn out. Minor amounts of stress may allow metals to even retain their shape.
Grains are the groups of regularly structured metallic atoms in a piece of metal. When moving or being deformed a lack of regularity in grain size prohibits the sliding of atoms thus causing more irregularities in deformation. Stress and pressure increase the amount of grains by breaking down large grains. The more individual grains there are the more likely there are to be irregularities and thus the more hard, or resistant to plastic deformation, change in the shape or size of an object due to an applied force, the metal is. The harder a metal is the more brittle, easily cracked or fractured, it becomes. The heating of metal resets the grains by invigorating the metallic atoms into a more regular shape, thus restoring malleability. Cold working makes metal harder by breaking up metal grains and producing smaller, more irregular ones. Work hardening is the increasing brittleness and hardness due to strain beyond a metal's yield point, or plastic deformation.
Now that we know what metals are, we know their atomic and microscopic structure, and how they move, we should look to who uses and used them. Humanity has made use of this amazingly versatile substance for thousands of years, and its existence has helped humanity to master his environment to the fullest. Much like fire, however, the discovery of this substance and its use is shrouded in mystery and a lack of knowledge. It is most likely that the discovery of metal, like fire, was an accident. One person noticed that a rock turned red in the fire more quickly than the others and that, through tedious experimentation, it could be shaped by being beaten with a stone into a crude blade or spear tip. The advantages of such a blade are obvious over its simple flint counter-part. Firstly, metal does not crack or chip with use, it only bends and thus is not completely ruined and can be repaired which is much less difficult than fashioning a completely new stone blade. Metal can also be honed into a sharper tip with much less skill. Metal can also be shaped with less than a fraction of the skill required to shape a flint blade.
Since around 7000-6000b.c.e. tribesmen in
The year 2800b.c.e. brings about another concept that must be defined and explained and that is alloys, a mixture containing two or more metallic elements or metallic and nonmetallic elements usually fused together or dissolving into each other when molten. Alloys are created in one of two ways, the first way being substitutional, and the second way being interstitutional. Interstitutional is the type of alloy formed when atoms of a smaller size are inserted into the gaps between metal atoms, making for a more dense, stronger compound, like bronze and steel. Substitutional is the second type of alloy and it is formed when atoms of a similar size replace metallic atoms in the metallic structure, such as sterling silver, brass, and pewter; this type of alloy is much harder to make. Alloys allow the combining of two or more substances with metal to create a substance with desired properties. Bronze is the first alloy discovered by man and remained the dominant material for tools in the Mediterranean,
Bronze, an interstitutional alloy, is made from the mixing of tin and copper, two soft metals that combine to form a significantly harder metal with the durability for much more diverse and extreme work. Bronze tools were first discovered in Sumer, a Mesopotamian civilization, in Ur, a city state of said civilization, around the year 2800b.c.e. Bronze spread to the Indus river valley civilization known as the Harrapan civilization (named after one of its cities) by the year 2500b.c.e. Bronze spread to west and central Europe to the predecessors of the Celts around the year 2000b.c.e.. The lack of production and avability of bronze limited its use to the wealthy and thus was mainly used as luxury items or weapons instead of tools. The Chinese discovered bronze around 1500b.c.e. completely separate from the nations of north Africa and Mesopotamia and
The creation of bronze required the finding of two rather rare metals in most parts of the world and was especially expensive. Iron was the solution to this problem as it was strong enough to be useful by itself. The only problem with iron is that it is found very imnpure in nature and could not be separated from ore by smelting due to the lack of means present. Copper and tin melt at 1300 degrees Celsius whereas iron melts only at 1528 degrees Celsius. The furnaces used to smelt bronze just couldn’t produce enough heat to smelt iron. As a result of the lack of means necessary to melt out the impurities of iron, the impurities had to be beaten out of the metal, which required a lot of time and energy and was dreadfully inefficient.
As a result of the ineffiecency of iron processing there was a five hundred year gap between when iron was discovered and used around 2000b.c.e. and when it was widely used around 1500b.c.e. The Hittites of Anatolia were the first to use iron as their artifacts indicate. Iron, like copper, was quickly replaced by its better alloy form known as steel.
Steel is an interstitutional alloy formed when iron is super heated with charcoal or some other high carbon fuel and then quickly cooled. During heating the iron atoms separate slightly and the carbon from the burning fuel is turned into gas, as the gas escapes some is caught between the expanded iron atoms, like fish in a net, and when the iron is cooled the carbon atoms are locked in and the iron is now steel. Steel is harder, less brittle, and thus better to use and easier to work with than iron. Thus steel was highly prized over iron but was not widely used until it could be effieciently produced.
Around the 11th century b.c.e. the iron age began in the middle east and spread out from Anatolia and the
In 1161b.c.e the Celts of Britannia built the first European iron foundry in
Europe and China continued to advance in metallurgy and chemistry and metal working and by 1709 Abraham Darby discovered that iron could be brought to smelting temperature by coke, a gray, hard porous substance formed from the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal, instead of coal. This discovery greatly advanced the production of steel by making fuel use more efficient and thus more steel could be made with less fuel.
Our knowledge of metals has greatly increased since 1784 and is far more comprehensive than need calls for to mention, but it is safe to say that humanity does not yet know everything about metals. Metals have been and will most likely always be a huge part of human life and an understanding of them is important for everyone.
