Perspectives

  • Issue 113 / September - October 2016



    Metals Have Character Too!

    Noah Weaver

    Whether in the form of cars, planes, or household appliances, we interact with metals almost every day. Despite the ubiquity of metals, most people never stop to think about their characters – or their differences in character.  
    Most people know metals from the Periodic Table, which consists of 118 elements, 92 of which are found in nature. A great majority of these elements are metals, for they have similar chemical properties. Although some metals such as iron, copper, gold, silver, and aluminum are commonly known, many other metals are not, even though they’re commonly found in everyday items. Lithium, for instance, is found in cardiac pacemakers. You probably know mercury, but did you know it’s used in street lights? Do you enjoy watching television? If so, you’ve benefited from yttrium, which is used in TV screens.



    Almost every element can be useful to people: every living and non-living thing is made-up of the 92 natural elements.
    Like all elements, different metals have different properties. As such, they have different melting points, and different degrees of hardness and conductivity.
    The reason these differences exist have to do with the number of protons and electrons in each metal’s atoms, as well as the atomic diameter, their intensity, and tendency to react.
    There are dramatic differences in the properties of different metals. Gallium (31Ga) has such a low melting point (29,7 0C) that it can melt in your hand, whereas tungsten (74W), which is used for the wiring in light bulbs, has as a melting point as high as 3410 0C. While sodium (11Na) is a metal so soft it can be cut with a knife, chrome (24Cr) is so hard that it can only be cut with diamond. While potassium (19K) has an instantaneous and very violent reaction when mixed with water, silver (47Ag) does not react to water at all.



    The fact that metals have different properties is a great advantage for their uses in different fields. A decrease or increase in the number of protons, a change in the speed of the electrons rotating around the nucleus, or a differentiation in the distance between the nucleus and the electrons, will change the properties of the metal.



    For a metal to be “plasticized” – for it can change shape without breaking – it must have atoms that can slide against one another. Thanks to this property, it is possible to shape steel on an anvil or to wring steel construction material. Otherwise, these metals would be useless materials which could not be made into wires or sheets. Thankfully, many metals were designed to be malleable.  



    Another quality given to metals is their ability to combine with other metals and form substances called alloys. These combinations develop different characteristics from their base metals. For instance, many metals have what are called “crystal gaps.” As such, they are not very strong in their pure state. But when combined with another metal to make an alloy, these gaps are filled by the atoms of other metals. The alloy thus becomes more durable. These new substances present different qualities than the individual metals that form the alloy. Some of the best known alloys are bronze (copper-tin), brass (copper-zinc), and solder (lead-tin). Alloys are commonly used for producing items with ideal physical properties for their intended field of use. For example, steel is an alloy of iron, and there are tens of different kinds of steel depending on the type and amount of other elements mixed with the iron. Although carbon is generally used when making steel, it is also possible to use metals like magnesium, chrome, vanadium, and wolfram. Thanks to being an alloy, steel has more advantageous qualities than iron, such as its hardness, being stainless, and its stress threshold.



    Alloys with shape-memory
    Certain alloys, after being altered by pressure or heat (martensitic state), have the ability to return to their original or initial shape (austenite state) when heated. The most widely used alloy with this “shape-memory” is “nitinol,” which is an alloy of nickel and titanium. If an item made from nitinol is heated beyond its limits, it will return to its original form.



    This “shape-memory” trait can be useful, including in unexpected ways, such as preventing strokes. Medical filters made from nitinol are planted in blood vessels. This filter is flattened before it is planted in the blood vessel, so when it enters the body, the body’s heat allows the nitinol to regain its original shape, thus catching any clots that pass through the vein and helping to lessen the likelihood of strokes or heart attacks.
    Shape-memory metals are now used as connection units, leakage preventers, pincers, and electric keys in a wide variety of industries. These metals are also used as construction materials.



    Iron – from the heavens
    For most of human history, iron has been the commonly used metal in the world. 95% of the metals used, in weight, consist of iron. Iron is so frequently used because it is abundant in nature, cheap, and can be made into many different alloys.
    Iron is also integral to the human body. The amount of iron in human body is, on average, equal to the amount of iron needed to produce a common nail. It is found in the structure of hemoglobin, and helps circulate oxygen throughout the body. Perhaps due to its importance, there is a chapter in the Qur’an named Hadid – or, Iron. The 25th verse of this chapter reads, “And We have sent down iron, in which is stern might and benefits for humankind, so that God may mark out those who help (the cause of) God and His Messengers, though they do not see Him. Surely God is All- Strong, All-Glorious with irresistible might” (Hadid 57:25).



    The expression “We have sent down” is also very interesting. Iron can only be formed in stars much bigger than the sun, by heat that reaches a few hundred million degrees Celsius. The nearly 15 million 0C heat in the sun is not sufficient for forming iron atoms. When stars supernova, the meteors containing iron explode out into space, and keep soaring until they are caught by the gravity of a celestial body. There are other elements that originate in deep space, too, such as Nickel (59Ni). These elements are “sent down” to us from the heavens.



    Another opinion about iron being “sent down” is as follows: thousands of meteors of different sizes hit our atmosphere every day and fall to the earth as dust. The iron atoms abundantly found in such dust are the nutrition for the plankton in the world’s oceans. Plankton, which play a huge role in the entire world’s food chain, get the iron they need for photosynthesis from this space dust.  
    In our everyday lives, we tend to take most things for granted and ignore the amazing reality of our world. We should stop sometimes to think about how remarkable it is that some of the metals we use are produced in remote stars and then “sent down” to us by grace.


    Reference
    http://www.ajnr.org/content/28/5/872.full


     


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