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Everything Matters - Tales From The Periodic Table Tin

Welcome to Everything Matters - Tales From The Periodic Table. I’m your host,
Ron Hipschman and today we’re going to talk about the element Tin. (Shows
element)

Here we see the beautiful periodic table produced by Theodore Gray.
Incidentally, Theo has written one of my favorite *** books called “The
Elements” which you can pick up from the on-line Exploratorium Store if you want
your own copy! Check out his fantastic website, periodictable.com.  *** Tin is
the 50th element in the periodic table. Its atomic number is 50 because that’s
how many protons are in its nucleus, and THAT is what distinguishes it as a
unique element.

We have no idea who discovered Tin, but it may have been found as early as 3000
or 3500 BCE. It was probably not known as an independent element that early, but
rather in *** combination with copper. More on this combination, called "bronze"
later…

There are about 9 elements discovered before written records. Here you see which
ones. Sulphur, Iron, Copper, Silver, Tin, Antimony, Gold, Mercury and Lead.
These elements were discovered so early because many of them occur in nature in
their native state.

Tin derives its name from the Latin name stannum which originally meant an alloy
of Silver and Lead. Of course, we know that Tin is neither Silver or Lead, but
rather, a unique element on its own. Stannum gives us the chemical symbol ***
"Sn" for Tin, and we still use names like "Stannous Chloride" for chemical
compounds that contain Tin. Through unknown translations Stannum became ***
"Zinn" in German, or *** "tenn" in Swedish, and finally, by the 4th century, ***
"Tin" from the Dutch.

Tin has two main allotropes. Allotropes are two or more different physical forms
in which an element can exist at room temperature - *** like graphite and
diamond for the element Carbon. *** Tin has two allotropes, the first stable
allotrope is *** ?-tin (on the right), a silvery-white, malleable metal which
has a body-centered tetragonal crystal structure. At lower temperatures, ?-tin
transforms into the less-dense *** grey ?-tin (on the left), which has a diamond
cubic crystal structure. Both are still pure Tin, but the atoms have a different
arrangement. *** Here is a sample that has both allotropes. You can see both the
brighter ?-tin and grayer ?-tin.

You can turn silvery beta-Tin into darker and more brittle alpha-Tin simply by
lowering its temperature to less than 13.2° Celcius (about 56°F). You’ll notice
that the volume of alpha-Tin is larger - 27% larger to be precise. This movie is
sped up by a factor of 28. This process is called "Tin pest". It’s also been
known as "Tin disease", "Tin blight", or even "Tin leprosy". In 1912, Robert
Scott trudged toward the South Pole only to find that previously stashed cans of
kerosene fuel were empty. The cans had been soldered with Tin. In the low
antarctic temperatures, it’s hypothesized that the soft and ductile Tin solder
holding the cans together, had turned to brittle alpha-Tin, allowing the
contents to leak out.

Another interesting effect can be HEARD when a bar of Tin is bent. The crystal
structure is distorted and the dislocation of the crystals can be heard as a
crackling sound, also called a "Tin cry".

The Universe produces most of the Tin (69%) in dying low-mass stars, with
smaller amounts (31%) produced in merging neutron stars (pretty exotic…).

On Earth, Tin is obtained chiefly from the mineral Cassiterite, which contains
stannic oxide, SnO2. Cassiterite is the the only commercially important source
of tin.

The main suppliers of Tin are, China, producing 42% of the Tin in the world,
followed by Indonesia with 28%, then Peru, Bolivia, and others. In the U.S. we
import 77% of the Tin we use.

The American Chemical Society’s “Endangered Element List” places Tin as "Limited
Availability - Future Risk to Supply", so we need to keep our eye on this, and
be sure to recycle our Tin. This rating indicates the relative risk to the
supply of Tin required to maintain our current economy and lifestyle.

How common is Tin? Not super common, but not super rare either. It's the 48th
most common element in the universe, *** the 39th most common element in the
Sun, *** the 38th most common element in meteorites. *** In the earth's crust,
it holds 47th place - about 2 parts per million, compared with 75 parts per
million for Zinc, and 50 parts per million for Copper. *** In the oceans it's
51st most common element, and *** in humans, surprisingly, it's the 26th most
common element.

The current cost of Tin is about $18 per kilogram. *** Over the past couple
years, that price has gone up and down, but not wildly, from a high of about $22
per kilogram to a COVID-19 low of about $13 per kilogram

If we compare the size of the Tin atom to that of Hydrogen we’d see something
like this. The Tin atom is a little less than 3 times the size of Hydrogen. A
picometer is *** a trillionth of a meter. Atoms are small.

Here are atom sizes sorted from largest (Cesium on the left) to smallest (Helium
on the right). *** Tin is a mid-size atom

Each element has many different forms. For each specific element, the number of
protons in the nucleus is the same - 50 protons for Tin - but there can be
different numbers of neutrons in the nucleus. All these different forms, called
*** “isotopes", are chemically identical to each other, but with slightly
different weights. The number you see next to the chemical symbol is the total
number of protons and neutrons in the nucleus. There are 39 isotopes of Tin and
of these *** there are ten stable, non-radioactive isotopes - more stable
isotopes than any other element. These ten stable isotopes *** are found in
different proportions in nature - from less than 1/10% to almost 33%. By the
way, the word "isotope" comes from the greek *** "isos" meaning "same or equal"
and *** "topos" meaning "place" since all these various forms of *** Tin occupy
the same place in the periodic table.

Of the radioactive isotopes of Tin, these are the longest lived, the ones with
half-lives over 1 hour. More about half-lives in the next slide. As you can see,
the longest half life here is 230,000 years for 126Sn. Even 230,000 years is but
a blink compared to the age of the universe, so any 126Sn (or the other tin
isotopes) cannot be left over from the Big Bang 13.7 billion years ago. These
isotopes must be manufactured in stars or reactors.

What’s a half-life? This graph shows an exponential decreasing curve. As an
example, say we start with *** 1024 atoms of the an isotope from the previous
slide (you’ll see why I chose 1024 atoms - hint: it’s a power of 2 and we’ll be
doing a lot of divisions by 2). If you wait one half-life, half of your isotope
will decay, and you’ll have ***512 atoms left. If you wait one more half-life,
half of that half decays, leaving you with one quarter of the original 1024 or
*** 256 atoms. Another half-life, half as many again, or *** 128 atoms. ***And
so on. After 10 half-lives you’ll have about 1/1000th of your original amount.
By the way, notice that there’s one remaining atom after 10 half-lives. If you
waited one MORE half-life your remaining atom would have a 50-50 chance of
decaying in that time.

Tin is moderately dense at 7.31 grams per cubic centimeter, the exact same
density as our previous element, Indium. *** As a reminder, water has a density
of 1 gram per cubic centimeter. I’ve put up a couple more densities for
comparison. Iron is slightly denser than Tin at 7.89 grams per cubic centimeter.

Here is a graph of the elements from highest density to lowest density. When we
do this talk at the Exploratorium we have a set of *** blocks so you can feel
density for yourself, but we’ll have to wait to do this until we’re back in the
museum. Our set of blocks have a wide range of densities, *** with the densest
at Tungsten, to Lead, to Copper, to Iron, to Titanium, to Aluminum to Magnesium
(we also have plastic and wood blocks, but those are not technically elements…)
Again, *** Tin’s Density (the magenta circle) is 7.31 gm/cm3 and is the 44th
densest element.

Tin has the 78th highest melting point. *** A fairly low 232° Celsius (or 450°
F). There are only 11 other solid elements with lower melting points. As you’ll
see in a bit, because of this low melting point, Tin is used in some important
applications, like soldering.

Tin has the *** 46th highest boiling point at 2602° Celsius. That’s *** 2370°C
above its melting point of 232°C. A pretty big difference between melting an
boiling.

Tin has the 16th highest thermal expansion rate. It expands *** 1 part in 45,454
for every °Celsius in temperature rise. That means that if you had, say, a 1
meter bar of Tin, it would get longer by about 22/10,000 of a meter (or 2/10 of
a millimeter) when you raised its temperature by only 1° Celsius. That doesn’t
seem like much, but it would add up when you change the temperature
significantly or have a long bar of tin. ***Iron expands about half as much for
the same temperature change.

Tin is VERY soft, with a hardness of only *** 1.5 on Mohs scale of hardness.
Even though it’s on the same line as our previous element, Indium, Tin is a bit
harder. Mohs scale is a bit rough…

In this chart of hardness, sorted from hardest (Boron, on the left) to softest
(Cesium, on the right), *** Tin is the 52nd hardest, or rather, the 15th softest
element. You could, with some difficulty, cut it with a knife.

Tin is the *** 26th best conductor of electricity. Not bad, but not good enough
to use it for this quality, although Tin does become a superconductor at 3.72
degrees above absolute zero, a better conductor than any element at room
temperature.

It’s the *** 28th best conductor of heat. Again, not bad, but not excellent
either.

From our Periodic Table of the *** Spectra, we see that Tin displays a variety
of emission lines, but lacks much on the blue and violet end of the spectrum.

Putting a solution containing Tin into a flame displays a beautiful blue color,
which actually surprised me given the lack of blue emission lines in its
spectrum. *** I guess that it’s easier to excite this line in its spectrum from
unexcited room temperature atoms

Let’s take a look at some of the major uses for Tin. There are many.

These are the primary uses for Tin. The largest, by far, is in soldering,
followed by plating, chemical uses, alloying, glass production, and other uses.
Let’s take a look at these.

Because of Tin’s low melting point, it’s used extensively in the electronics
industry to solder metal parts together. Here you see electronic parts being
soldered to copper pads on a prototyping circuit board. *** Plumbers use solder
for the same purpose  - to solder together copper pipes. Up until 1986, *** most
solder contained 60% Tin and 40% Lead. Many people thought that soldering
together drinking-water pipes with Lead-containg solder may not be a very good
idea, so that was outlawed, and, in 2006, many countries and California ***
banned Lead in electronic solder too, because it was appearing in land-fills. We
now use Lead-free solder that is a combination of 99% Tin, 0.3% Silver, and 0.7%
Copper.

Speaking of low melting points, let’s look at a couple more interesting
examples. Field’s metal, named after its inventor, Simon Quellen Field, is a ***
eutectic alloy. The word "eutectic" comes from the Greek *** "??" (eu meaning
*** "well") and *** "?????" (t?xis - not the state - meaning *** "melting".
Well, maybe not a bad description of the state after all, but I digress). A
eutectic alloy melts at a temperature lower than the melting point of any its
ingredients. Note that all the ingredients of Field’s metal melt above 156°
Celsius. Field’s metal is solid at room temperature, but becomes liquid *** at
the low temperature of approximately 62°Celsius (or 144°F), less than ? the
lowest melting temperature of any of its ingredients. It’s an *** alloy of
Indium, Bismuth, and Tin, in the percentages you see here.

An even more impressive example of a low melting eutectic alloy is Galinstan,
which gets its name from its ingredients - *** Gallium, *** Indium and *** Tin.
Remember, the old name for Tin was from the Latin stannum (the "stan" in
Galinstan). Galinstan is an alloy of 68.5% Gallium, 21.5% Indium, and 10% Tin.
It remains a liquid below the freezing point of water. Its melting point *** is
?19°Celsius ( or ?2°F). Galinstan can be substituted for Mercury in ***
thermometers since it’s now illegal to use toxic Mercury in medical
thermometers.

Tin plating, the second largest use of Tin, is perhaps most familiar in the
canning of food. The cans themselves are made of steel, and we all know that
steel has a rusting problem. By plating the steel with Tin, which is non-toxic
in its metallic state, the cans no longer rust. *** So calling these "Tin cans"
is a bit of a misnomer, but there IS Tin there!

Tin cans aren’t the only food-related tin item. Here is a beautiful Tin cup from
Theodore’s Gray’s amazing element collection.

One of the chemical uses of Tin is in toothpaste and mouth-rinse in the form of
*** stannous fluoride. Stannous fluoride is added to these products as an
anti-bacterial agent that's clinically proven to protect against gingivitis,
plaque and tooth sensitivity in addition to preventing cavities (and is, no
doubt, approved by 4 out of 5 dentists). Some products substitute sodium
fluoride which only protects against cavities.

With its low melting point and low toxicity, tin is a good candidate to use in
casting. Here we see classic "tin soldiers", and a tin caterpillar for good
measure.

Tin coins have even been known, though with the easy melting and casting
properties of Tin, they were probably simple to counterfeit. I have no idea of
the monetary value of these coins, but I’m assuming that they are worth less
than the cost of the tin they were made from, making counterfeiting
uneconomical. The other problem with Tin coins is Tin pest. If you keep your Tin
money at a low temperature, you won’t have any after a while, just alpha-Tin
crumbles!

Aside from the Eutectic alloys we’ve previously seen, Tin has been an important
ingredient in many metals since ancient times. Here you see two bronze examples,
the Houmuwu ding or, or sacrificial vessel on the left - the largest surviving
piece of bronze-ware from around 1100 BCE, and on the right, we have a bronze
statuette of Jupiter from the 2nd half of 2nd century C.E.. In the middle, a
different alloy, a pewter mug.

The first tin alloy used on a large scale was bronze, as early as 3000 BC. The
giant Bronze dirk from 1500–1300 BCE on the left, is a very early example.
Bronze is still used in contemporary statuary, such as Rodin’s "The Thinker",
which you can visit at the Legion of Honor here in San Francisco’s Lincoln Park.
Bronze is an alloy of *** about 87.5% Copper and 12.5% Tin, though the
percentages can vary depending on intended use. The addition of Tin, and
sometimes other elements to copper, created a metal that was harder, easier to
cast, and more durable than any of its constituent ingredients, and harder than
any other metal up to that point. This invention led to the "Bronze Age".

Pewter is a malleable metal alloy composed of 85–99% tin, mixed with
approximately 5–10% antimony, 2% copper, bismuth, and sometimes silver.

An extremely important use of Tin is in the manufacture of plate glass. Until
1959, it was fairly difficult to manufacture very flat glass with parallel
sides. In that year the "float glass process" was invented. And it uses Tin,
lots of Tin, as part of the glass forming process.

*** Raw ingredients are combined and added to massive furnaces at the start of
the process to blend and melt what becomes glass. A ribbon of glass exits the
furnace to the Tin float bath. Glass is less dense than Tin, so like oil and
water, the glass ribbon floats on top of the perfectly flat molten Tin surface.
It’s drawn through the bath by a set of rollers on each side of the ribbon.
Pulling the glass faster thins the ribbon. Slowing the rollers makes a thicker
sheet. It exits the Tin bath into the what’s called the lehr, which in the next
800 feet gradually cools the glass, reducing stresses within the sheet, creating
a strong piece of glass. The ribbon is then inspected, cut to size, packed and
shipped to the end user.

Here’s a photo of the glass ribbon passing through the tin float bath. You can’t
really see the Tin, since it’s glowing the same red color as everything else in
the chamber, but you can see the toothed wheels that draw the glass along.

Given the linear nature of the float glass process these plants tend to be very
long, usually extending a quarter mile or more. There are about 450 of these
float glass lines in the world, producing over a million tons of glass every
year. None of that would be possible without Tin.

This glass finds its way into architectural uses, *** the automotive industry,
*** solar panel manufacturing, and the making of glass for *** display panels
like the one you’re looking at right now on your *** phone, tablet, computer, or
television.

Speaking of display panels, Tin plays another important role in those. ***
Indium Tin Oxide, or ITO as it’s referred to in the industry, is a clear
conductor of electricity. Let me say that again - it’s a conductor that you can
see through! It’s used in applications such as liquid crystal panels. You see an
extreme closeup of an LCD panel on the bottom right, with live video from my
television on the top. Let’s look at a *** cross section. Electrical current
must flow between the two light-blue electrodes in front and behind the liquid
crystals. The liquid crystals can switch between transparent and opaque when
placed between the transparent ITO electrodes. Light from the from the *** light
source on the back-side of the panel must pass through the ITO electrodes and
the liquid crystals. Normal conductors, like copper and aluminum are opaque and
would block the light. *** Indium Tin Oxide is both conductive AND transparent,
so it’s a natural for this application, allowing the light past the liquid
crystals and then *** through the red, green, or in this case, blue colored
filter in front, *** to get to us.

Another application of LCDs is privacy glass that can be almost magically
switched from opaque to transparent. This example, in the bathroom, is from
Intelligent Glass. You can’t do this without the transparent electrodes made
from Indium Tin Oxide within those panels. By the way, this isn’t cheap - around
$50 per square foot, so this example would cost you about $8000!

Before the laser printer, or the ink-jet printer, letters were placed on the
page by pressing inked pieces of metal with letters molded into them to the
paper page. Each letter was laboriously placed, one at a time, *** into a frame,
called a "chase". These letters or "type" as they were called, were made from a
low-melting, but strong alloy consisting of *** 50 to 86% Lead, *** 11 to 30%
Antimony, and *** 3 to 20% Tin. The formula changed depending on usage.

If you ever went into a printer’s shop (my dad was in printing…) you’d see type
cabinets like these, *** with each drawer containing a specific font at a
certain font-size. The drawers were *** organized in some way that made sense to
printers, but I could never figure out.

If you ever went into a printer’s shop (my dad was in printing…) you’d see type
cabinets like these, *** with each drawer containing a specific font at a
certain font-size. The drawers were *** organized in some way that made sense to
printers, but I could never figure out.

Slightly less laborious, were Linotype machines. Here, the operator sat in front
of a keyboard and typed the text. Liquid type-metal was instantly cast into ***
lines of type that were then mounted in the printing frames. Far less work than
dealing with each letter individually.

Tin plays no natural biological role but is found in the human body in small
quantities, usually from the environment. Metallic Tin is relatively non-toxic
and passes through the digestive system with extremely little absorption.
However, Indium Tin Oxide, used in those LCD panels, can harm the pulmonary and
immune systems, so exposure in LCD manufacturing must be monitored.

We’ll end today’s talk with Mary Soon Lee’s elemental haiku about Tin:

Your magic number
a secret no one could guess
back in the Bronze Age.

Thank you for watching Everything Matters - Tales From The Periodic Table. The
next program in this series will examine *** another interesting element,
Antimony. We hope you’ll join us.

This program, like all Exploratorium programs, is only possible because of
donors like you. We know that this time is challenging, but If you can, help us
keep educational content like this free and accessible to all by *** donating
today at www.exploratorium.edu/connect. Thank you.