ZINC

Name: Zinc

Symbol: Zn

Group: 12

Period: 4

Block: d

Category: Transition Metals

Atomic Number: 30

Atomic Mass: 65.38 u

Electrons per Shell: 2, 8, 18, 2

Electronegativity: 1.65

Density: 7.14 g/cc

Melting Point: 419.53°C

Boiling Point: 907°C

Thermal Conductivity: 120 W (m K)

Electrical Conductivity: 1.7 × 10^7 S/m

Magnetic Order: Diamagnetic

Ordinary State: Solid

Oxidation States: -2, 0, 1, 2

Mohs Hardness: 2.5

Hardness Vickers: No data

Brinell hardness: 412 MPa

Most stable isotopes: Zn-64 (49.2%), Zn-66 (27.7%), Zn-68 (18.5%), Zn-60 (0.6%)

Discoverer: Andreas Sigismund Margraaf, German, (1746) - disputed

There is a dispute about who, when, and how zinc was discovered. Being a relatively easy metal to obtain from its main mineral, sphalerite (ZnS), a sulfide easily reducible with coke, it is possible that the use of the metal is older than recorded history. Although it is not very abundant, it is believed to be so, this is because, like iron and copper, and unlike titanium or aluminum, it is found concentrated. That is, some metals are very abundant, such as titanium, but are found "diffused" in very complex and difficult-to-reduce minerals, while others, such as zinc itself (or lead, tin, and copper, to name a few examples) occur in normally binary minerals (sulfides) that are reduced with coke. This, coupled with the fact that it has a low melting point, is easy to manipulate, and is moderately resistant to oxygen and water vapor, leads us to believe that it is indeed an "ancient" metal (in the sense of its earliest use).

The main problem in this regard is that, for some reason, zinc was little known in Europe, even at the height of the Middle Ages. This is particularly important when considering whether it was known or not, since alchemy, as a discipline itself, has an Arabic origin, not a European one, as is often thought. This confusion stems from the fact that the majority of studies and works that have come down to us are largely written in Latin or Germanic languages, which adopted this knowledge and took it to the next level. So much so that, as you already know, modern chemistry derives directly from alchemy, even though its main objective was the transmutation of the less noble elements into gold and silver, as well as the synthesis (or production) of the Philosopher's Stone, both of which were more prominent among European alchemists than among Arabs.

Zinc, unlike the so-called "seven metals" (iron, copper, silver, gold, tin, lead, and mercury), known since ancient times, at least in the Western world, is not referenced in most major alchemical treatises. Antimony, for example, is even less important than zinc, yet it possessed its own alchemical symbol. Zinc is a relatively late discovery, and its discovery is credited to the German Andreas Margraaf, who supposedly identified it as a unique element in 1746.

On the other hand, many argue that it was in India, around the year 1200 (in the Middle Ages), that not only is it mentioned several times, but its properties are also described very accurately.

Personally, I find it hard to believe that zinc was "discovered" so late, especially considering that, as I said before, it is an easy metal to obtain: it doesn't require many resources.

The most logical explanation for why it doesn't appear as a recognized unique element is that, due to its characteristics, it was most likely often confused with lead, antimony, and tin (especially the latter). The element's name, "Zinc," is of German origin and refers to the sharp crystals of the sorosilicate mineral known as calamine, which has a much more complex composition than sphalerite ("ZnS" vs. "Zn4Si2O7(OH)2·H2O"). Calamine is very famous, so much so that, I know, the metal is sometimes sold as "calamine" or "calamine metal" even today, when in reality, metallic zinc and calamine have nothing to do with each other, one being an element in itself and the other a mineral of the metal, with completely different characteristics.

Another reason that possibly explains why the metal appeared (or was recognized) so late is that its main use is as the primary alloying agent for copper, just as tin is. Bronze is believed to be much older than brass, but brass is not as modern as it might seem in a Western context, both for Europeans and for the nations founded by them, such as the Americas.

In any case, zinc is zinc, not calamine, tin, or antimony, but an element in its own right.

Zinc is a soft metal, yet it is not very malleable and non-ductile. It is difficult to obtain sheets of the metal by hammering, as it is brittle and fractures easily. Obtaining pure zinc wire is virtually impossible, although, as I mentioned before, this contrasts with the fact that its hardness (in the sense of its resistance to abrasion) is very low, 2.5 Mohs (even copper is harder in this regard). Zinc, therefore, has very few structural applications, as it is "weak" in every sense. However, it is used in some applications where rigidity or impact resistance are not a priority, such as applications that fall into the "low-responsibility" category, so called because they do not involve great stress, as would be the case with typical steel. It is obtained primarily from sulfide, sphalerite (ZnS), and to a lesser extent from other minerals, such as calamine, very popular in Europe (particularly in Spain, where it has been known for centuries). It is a typical chalcogen: although it oxidizes spontaneously, its preferred element is sulfur (as evidenced by the chemical composition of most of its minerals). In this respect, it resembles silver, lead, and copper. They are often found together in the ores from the mining operations of these metals. Zinc is inexpensive and is widely used in industry for many applications.

It is one of the few metals that has a "blue" tint pronounced enough to distinguish it from the rest; after all, it is still silvery-gray. When very pure and uncorroded, it exhibits this characteristic hue that makes it more similar to freshly smelted lead and, to a lesser extent, to osmium. The similarities with these two metals end there, since Zinc shares more chemical properties with alkaline earth elements such as Magnesium, and p-block (post-transition) metals such as Aluminum, with which it is alloyed, producing alloys with excellent mechanical properties.

Zinc's nature is unique among the Period 4 metals of the Periodic Table, as it resembles the p-block metals Magnesium and Aluminum much more closely than typical transition metals: unlike these, it has a low melting point, is brittle, and has little ductility or malleability. It alloys with difficulty with transition metals (iron is impossible, let alone titanium, among others). Copper has the greatest affinity for it, along with Silver, Gold, and the p-block metals with which it alloys extremely easily.

It is chemically similar to Magnesium: it has two valence electrons, and its behavior in this area is very similar. They also share oxidation states.

Until very recently, both zinc and the rest of the metals in group 12 of the Periodic Table "belonged" to the transition metals; however, they have recently been included as post-transition metals (for the reasons I explained above). As far as I'm concerned, it exhibits intermediate properties between both groups, since while physically it resembles a p-block metal or even a metalloid (and chemically, magnesium), it is still a member of the d-block, which contains the transition metals.

Zinc, continuing its tendency to stand alone, exhibits a lower electronegativity than copper, as well as a higher tendency to corrode than any Period 4 metal, including iron. This is vitally important to understand how it is possible for it to be so effective in protecting pieces made from this metal, mostly steel and, to a lesser extent, cast iron, used strictly for ornamental purposes or with little mechanical stress.

Zinc does not oxidize the way iron does: it forms a passive layer that is quite resistant and is, in fact, widely used in the steel industry for coating non-stainless steel. Zinc not only acts as a barrier, but also, having a more negative electrode potential index than iron (the main component of steel), yields first to a galvanic cell. What does this mean?

If we immerse metallic zinc and non-stainless iron/steel in an aqueous solution (fresh or saline, only the reaction rate will change), we will see how zinc corrodes more quickly. This means that it is chemically less noble than iron, something that can lead to confusion, since raw zinc "remains" with its passivating layer, while iron/steel corrodes rapidly, forming the characteristic rust of varying colors, ranging from red, dark red, carmine, or black, depending on factors such as the presence or absence of water vapor (a source of hydrogen) and the oxidation state.

Zinc, therefore, is considered to have little resistance to corrosion, and indeed it is; it is only stable in air and fresh water, but it yields vigorously to aggressive media, both oxidizing and reducing. However, resistance to oxidation and sulfation by conventional means, such as in the case of steel and copper-based alloys, is quite good, so it is used to coat steel, in what is called "steel coating." "Coating" refers to the act of depositing a layer of metal over "bare steel," nothing like removing an animal's testicles.

Steel coating is the third most effective method of protecting non-stainless steel after chrome and nickel plating. The more correct term would be "zinc plating" or "zinc plated," but the much better sounding "coating" is non-negotiable, ergo it is preferred. Likewise, the Royal Spanish Academy prefers "zinc" over "zinc," but accepts both as good. The replacement of the zeta is an attempt to Hispanize the name (this happens even with personal names, as is the case with kings, for example: "William" would be "Guillermo." This is done to facilitate the pronunciation of names, and is done not only by the RAE (Royal Spanish Academy of Spanish Language) but also by other European linguistic academies, to the point that the elements are called by various names depending on the country), but as I mentioned before, both terms are accepted. Something similar formerly happened with Wolfram, which was sometimes referred to as Wolfram or Tungsten (the latter especially in Latin America in accordance with the literature that mostly originates from North America). There is also the case of Tantalum, which can alternatively be called "Tántalo" (Tantal), or Niobium, which was formerly called "Columbio" (Columbium) in honor of Columbus. Beyond the etymological differences, the element remains the same.

Zinc in its pure form has no significant structural applications (at least, not in its pure form). It is used for coating steel, especially (though not exclusively) in corrugated steel roofs, so popular in the past and even today in some less developed countries. They are effective, inexpensive, and have a long lifespan. The famous "zinc roof" is actually zinc-coated steel, not metallic zinc.

Another use of the metal in its pure form is in the manufacture of galvanic cells. It is used interchangeably in the chemical and electrical industries for these purposes.

In its highly pure form, it has a main alloy, called "zamak," which we will discuss later. Along with tin, indium, lead, and bismuth (basically the most popular members of the p-block group of metals), it forms part of the so-called "white metals" or "pot metals" related to tin and its main uses (such as replacing silver). Zinc has a great advantage over the stronger transition metals in that it is easy to melt, and therefore, items such as glasses, cutlery, plates, toys, buttons, etc. are obtained from Zinc and other similar metals that share a low melting point with it and are therefore easy to recycle, making them the preferred material for practically any small metallic object that, as I have said repeatedly, does not necessarily have to be "strong," as long as it does have the virtue of being moderately resistant to corrosion (enough to withstand dry and humid air or even fresh and even salt water). A practical example is the "zippers" on jeans, backpacks, etc. I bet that at some point, if you have had problems with one that has blocked (jammed) and you pull on it with enough force (possibly alienated by the situation), you will find yourself in a few minutes with part of the zipper in your hand: you have ripped off the knob without realizing it. This is because zinc, even in an alloyed form (as is the case with these products), is, as I've told you, extremely weak and therefore finds no significant uses in its solid form, even in an alloyed form. What is an advantage in some areas (producing thousands of pieces of zippers in the textile industry for closures, buttons, etc.) is advantageous in some areas and a loser in others. What I'm trying to do is show you why it isn't used in its solid form. I call "solid" any piece that has a use with the minimum resistance necessary to withstand mechanical stress. I suppose it goes without saying that zinc alloys, like pure metal, are extremely sensitive to heat (they weaken quickly), even more so than pewter (the quintessential cheap "white metal" alloy based on tin), which of course is much more valuable than any "zamak." Please don't think I'm disrespecting it.

In metallurgy, zinc is much more important as an accompanying metal than as a base metal itself. It is the main component of brass, the most important industrial alternative to bronze (I always say it and will continue to say it: in the United States it is more widely used than bronze), and also of aluminum alloys. No element, metallic or not, hardens aluminum the way zinc does. The toughest aluminum-based alloys are precisely those grades in which the zinc content predominates, although all of these contain significant percentages of copper, iron, magnesium, etc., depending on their intended use.

Zinc's compatibility is not broad: it mixes well with copper, aluminum (in small percentages), silver, gold, and P-block metals, but not with typical transition metals such as those found in steel or even iron itself, with which it is not compatible (they do not form alloys).

By far, the main user of zinc as an alloying agent is copper. It produces brass, the alloy we studied previously, which is any mixture of these two metals where the zinc percentage ranges from 10% to 45% (although both are extreme, the "standard" range is between 25% and 40%).

Zinc mechanically improves pure copper, increasing its toughness and hardness, while maintaining ductility and malleability far superior to any type of steel, a typical sign of copper-based alloys. Likewise, zinc gives the alloy a characteristic golden color, which has historically been used for strictly ornamental purposes as a replacement for gold.

As always, a saturation of zinc in the mixture (around 60% or more) should not be considered brass per se, but rather an intermediate alloy between it and another. Such a quantity of zinc goes from hardening copper to making it brittle, so this extreme is not usually touched.

The second main user of zinc is aluminum. It is used in virtually all alloys of this metal, even in small doses. The effect of zinc on aluminum is like that of no other metal: it increases toughness to such an extent that some aluminum alloys have even replaced steel in structural uses. I must clarify, however, that saying that aluminum or its combinations are mechanically superior to steel is not only a very abstract statement, but also fallacious (false). It's like always, people do a bit of research and publish headlines like: "They discover an aluminum alloy stronger than steel." What aluminum alloy? What grade of steel? They don't even know the difference between steel and iron, how could they possibly know what they're talking about?

Interestingly, iron often accompanies zinc and copper in small percentages in many aluminum-based or aluminum-magnesium alloys.