Sodium - Tales from the Periodic Table

Added: 2026-05-08

[00:00:01][music] >> Welcome to Tails from the periodic table. I'm your host, Ron Hypsehman, and today we're going to talk about the element sodium. These are beautiful untarnished lumps of sodium kept under oil or kerosene, and I have a sample right here as well, and this was sealed in the vial very shortly after it was harvested from a larger block. So, you can see this is also very untarnished.

[00:00:36]Let's get back to the slides. I can show you this a bit closer. Here we go.

[00:00:40]Here's that vial just thrown on my scanner, and we can look at it even closer, and you can see these are nice shiny lumps.

[00:00:50]Here we see the beautiful periodic table produced by Theodore Gray.

[00:00:54]As I've mentioned in previous episodes, Theo has written one of my favorite books called The Elements, which I encourage you to pick up. Check out his fantastic website periodictable.com.

[00:01:08]Sodium is the 11th element in the periodic table. Its atomic number is 11 because that's how many protons are in its nucleus, and that is what distinguishes it as a unique element.

[00:01:23]Sodium metal was first isolated by Sir Humphry Davy in 1807 by the electrolysis of sodium hydroxide.

[00:01:33]In electrolysis, you separate components of a solution with electricity. Here, you see water being separated into hydrogen on the left and oxygen on the right. Since water is H2O, there is twice as much hydrogen being generated as oxygen.

[00:01:55]While you could dissolve sodium hydroxide in water and do electrolysis, any sodium collected on the negative electrode would immediately react with the water. So, Davy melted pure sodium hydroxide and performed electrolysis on the melt.

[00:02:14]Sodium hydroxide melts at about 320° C or about 608° F.

[00:02:22]So, this is not a trivial experiment.

[00:02:26]Into the melted sodium hydroxide, he placed two chemically inert platinum electrodes connected to the newly invented voltaic pile. One electrode was charged negatively, and the other was charged positively. The positive sodium ions are pulled to the negative electrode and the OH hydroxyl ions toward the positive electrodes.

[00:02:53]Sodium metal gathers at the negative electrode, and the hydroxyl ions decompose at the positive electrode to water and oxygen gas. Here's that chemical formula for those who are interested. If you'd like to see a video of this being done, check out Scrap Science's video here on YouTube.

[00:03:18]Sodium is a common element and is relatively inexpensive, costing you between 100 and 200 dollars per kilogram in small quantities. However, it's a bit more expensive than you might expect because it takes a lot of electricity to make, and it's dangerous to package and transport.

[00:03:40]Estimates are around 100,000 metric tons of sodium metal are produced every year worldwide with major production in China, India, and the US.

[00:03:52]Just a note, most sodium metal is now produced by electrolyzing sodium chloride, common table salt, rather than Davy's method using sodium hydroxide.

[00:04:03]Same idea, though.

[00:04:05]100,000 metric tons of sodium would be a cube 10.1 meters on a side.

[00:04:14]Let's throw an average person in there for comparison. That's a lot of sodium metal given the fact that the metal, as opposed to its chemical compounds, has limited uses.

[00:04:27]Sir Humphry Davy was familiar with soda ash, which we now know as sodium carbonate. The soda part of that comes from Arabic suda or Latin sodanum.

[00:04:41]Hence, he named the element sodium.

[00:04:47]Jöns Jacob Berzelius invented the system of one or two-letter chemical symbols.

[00:04:53]He took the Egyptian name for sodium carbonate, natron, and used the Na from that as his symbol for sodium, as you see here in the formula for sodium carbonate. Unfortunate, since Sd was available at the time and would have been easier to recognize and remember.

[00:05:16]The elements on the left side of the table all have an outer shell with only one electron. They like to get rid of the single electron to expose the full outer shell beneath.

[00:05:29]These elements, the alkali metals, are all highly reactive because of that one outer electron. This is where we find this month's element, sodium.

[00:05:42]I'll return to the alkali metals in a moment, but let's look at a couple of other groups. First, the noble gases in the far right column of the periodic table. The noble gases over on the right side of the table have full outer electron shells and are pretty much inert, not wanting to participate in chemical reactions. They neither want to lose, gain, or share an electron. Those gases are helium, neon, argon, krypton, xenon, radioactive radon, and the newly synthesized element 118, oganesson.

[00:06:25]Here are the first few of those noble gases, helium, neon, and argon, with their complete outer shells.

[00:06:35]Next to the noble gases is a column of elements very different from their neighbors called the halogens. These all have one electron missing from their outer shell compared to the elements to their right.

[00:06:50]These are very, very chemically active.

[00:06:53]They want to grab another electron to complete their outer electron shells, then masquerading as a noble gas.

[00:07:02]Those elements are fluorine, chlorine, bromine, iodine, radioactive astatine, and newly synthesized tennessine.

[00:07:14]And here are the first few of those, fluorine, chlorine, and iodine, all missing one electron from their outer shells.

[00:07:26]Let's return to the alkali metals. As I mentioned, these elements all have an outer shell with only one electron, which they love to get rid of to expose a full outer shell beneath. These elements are all highly reactive because of that one outer electron, but in almost an opposite sense than the halogens. The halogens want to acquire an electron, while the alkali metals want to shed one. This is where we find lithium, sodium, potassium, rubidium, cesium, and radioactive francium.

[00:08:06]And here are the first few of those, lithium, sodium, and potassium. See that one lone electron in the outer shell?

[00:08:17]Sodium is very light. Its density is only 0.968 g per cubic centimeter, less than that of water at 1 g per cubic centimeter.

[00:08:30]Sodium floats on water, as you'll see later on.

[00:08:34]I've put a few more element densities here, so you can compare.

[00:08:41]Here's a graph of the elements from highest density to lowest density. I have a set of blocks, so you can feel density for yourself in my live talks.

[00:08:52]My 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.

[00:09:09]I also have plastic and wood blocks, but those are not technically elements.

[00:09:14]Again, sodium's density is 0.968 g per cubic centimeter, near the bottom of the chart, the 14th least dense element, about half as dense as my magnesium.

[00:09:28]Sodium, as I mentioned, floats on water before it violently explodes.

[00:09:35]Sodium has a melting temperature of 97.72° C.

[00:09:41]That's 207.9° F.

[00:09:44]That's the 18th lowest melting point, near the bottom of the table. Sodium would melt in boiling water, though there are explosive reasons not to try that, as we'll see.

[00:09:57]Sodium boils at a much higher 883°C.

[00:10:03]That's 1621.4°F, giving it the 23rd lowest boiling point of the elements. That's 785.28°C above its melting point, its liquid range of temperatures.

[00:10:23]One of the subscribers to this channel, SillySad3198, thought it might be nice to see a graph of liquid temperature ranges from highest to lowest. So, here it is. The widest liquid temperature range is of Neptunium with a 3,356°C liquid temperature range. All the way down to Neon, which is liquid in only a 2.51°C range.

[00:10:54]Sodium is liquid within a 785.28°C range. Notice all the gaseous and liquid elements have very small liquid temperature ranges.

[00:11:09]If we compare the size of the sodium atom to that of hydrogen, we'd see something like this. The sodium atom is about 3.6 times larger than an atom of hydrogen.

[00:11:21]We'll look at the sizes of the other alkali metals in a bit.

[00:11:26]Here's sodium's electron structure, which we already covered. By the way, a picometer is a trillionth of a meter.

[00:11:34]Atoms are immensely small.

[00:11:38]Looking at all the element sizes, here we see them sorted from largest, Cesium at the top left, to smallest, Helium on the bottom right.

[00:11:49]The size of the sodium atom places it in the upper region of the chart, the 27th largest atom.

[00:11:56]If instead of sorting from biggest to smallest atom, we just put them in atomic number order, the order they appear in the periodic table, we get a different and informative view.

[00:12:10]Now we see peaks and valleys, periodic structure to the set of sizes. As I mentioned, we start with hydrogen at the lower left and make our way up through the periodic table. Here's sodium, a large atom up on the second peak. The big atoms sitting on all the peaks are the alkali metals, the largest atoms of their periodic table rows. This has to do with that one lone electron in the outer shell. It's held rather loosely.

[00:12:44]On the other hand, the noble gases sit at the bottom of all the valleys, the smallest atoms of their respective rows with their tightly held and complete outer shells.

[00:12:58]Sodium is really, really soft stuff, coming in at only 0.5 on Mohs scale of hardness. It's much softer than your fingernail, meaning you can scratch it, but I wouldn't.

[00:13:11]Interestingly, all the alkali metals are very, very soft as well. Notice sodium in a chemical form called halite is harder than the metal, about the same hardness as your fingernail.

[00:13:25]You will not be surprised to learn that Mohs scale was invented by a German geologist and mineralogist, Friedrich Mohs, in 1812.

[00:13:36]Here, I'll demonstrate just how soft sodium is as I prepare it for another demonstration you'll see later.

[00:13:44]Take some sodium here out of the kerosene. This is a little block of sodium. It's very, very soft metal. It's so soft I can cut it with a butter knife.

[00:13:56]That's actually a little bit You can see there it has a silvery surface to it.

[00:14:00]And I'm just going to cut off I'm going to cut off half that piece. So, I'm going to put that back in the kerosene and I'm going to cut half of that cuz I don't want to put too much into the liquid.

[00:14:13]The element sodium is very common compared to many other elements in the universe, coming in as the 15th most abundant element by mass. 2 g out of every 100,000 in the universe is sodium.

[00:14:27]There's twice as much in the sun at 4 g for every 100,000, also making it the 15th most abundant element there.

[00:14:37]137 times as abundant as in the sun, it's the 11th most common element in meteorites, making up 5 g out of every 100,000.

[00:14:48]Sodium is very common in the Earth's crust, making up 2.3% of the weight there, 2.3 g out of every 100, the seventh most abundant element by mass.

[00:15:03]Sodium reaches its highest ranking in the oceans, where it's the fourth most common element by mass, 1.1 g per 100.

[00:15:12]Given the ocean is salty and salt is sodium chloride, this may not be surprising.

[00:15:19]Lastly, given the fact that we are salty, too, it may not be unexpected it's the ninth most common element in our bodies, making up 1.4 g out of every 1,000.

[00:15:34]We can see the evolution of the elements through the history of the universe in this somewhat complicated version of the periodic table.

[00:15:43]Here, you see each element square with a tiny chart of its own, showing that element's growth over the age of the universe by various processes. Sodium is here.

[00:15:55]I understand this looks complicated, but let's look at just sodium a little closer. The horizontal axis of this square represents time from the Big Bang to now. The vertical axis shows the proportion of sodium created by various processes.

[00:16:14]About 85% is produced in core-collapse supernovae stars, the yellow area, and the other 15% is produced in dying lower mass stars, the magenta area. Notice the sodium produced in dying lower mass stars doesn't get started until later because these stars last much longer before they die.

[00:16:38]Let's lightly touch on these processes.

[00:16:43]There are two main ways the universe makes sodium. The first is in large stars in their senior years after they become red giants. Sodium here is created by a somewhat complicated process called the neon-sodium process that involves converting neon to sodium.

[00:17:04]At the end of a star's life, as hydrogen in the core runs out, the star collapses, heats, and sheds its outer layers.

[00:17:14]In the hot core, it can convert neon to sodium. This probably happened in M57, the Ring Nebula, about 1,600 years ago.

[00:17:25]This is how it appears today, visible in a small telescope, but not in color to the naked eye.

[00:17:33]Sodium can also be created in massive stars as they end their lives in a supernova, like you see here in M1, the Crab Nebula. This happened about 1,000 years ago.

[00:17:47]Here, colliding carbon nuclei combine to create sodium in a process called carbon burning.

[00:17:56]These nebulae are not to scale. If actually placed side by side at the same distance, they would look more like this. Even though the Ring Nebula has been expanding for 600 years more than the Crab the Crab was a much, much more violent event and it's expanding much faster. The Crab Nebula is now about 8.5 times as big as the much older Ring Nebula.

[00:18:28]The neon-sodium process is multi-step, building sodium from neon in large red giant stars.

[00:18:36]We start with neon-20, which can absorb a hydrogen nucleus, just a proton, really, and that becomes sodium-21 and a gamma ray.

[00:18:48]Now, sodium-21 is a radioactive isotope and has a half-life of only 22.455 seconds. It decays by giving off a positron, a positively charged antimatter electron.

[00:19:03]This transforms it into neon-21.

[00:19:07]This neon-21 then absorbs another proton, becoming sodium-22 with the emission of another gamma ray.

[00:19:16]Like before, this is a different radioactive isotope of sodium, this time with a half-life of 2.6019 years. It also decays by giving off a positron. This transmutates it into neon-22.

[00:19:35]Okay, we're almost there. Like before, this neon-22 absorbs another proton and finally becomes stable sodium-23 with the emission of that gamma ray again.

[00:19:50]The carbon burning process occurs in supernovae generated by stars over eight times the mass of our sun.

[00:19:58]This is the only place where billion degree temperatures occur.

[00:20:04]That's necessary for this reaction.

[00:20:06]This is a bit simpler. Here, already existing carbon nuclei combine to form sodium 23 and an extra hydrogen nucleus, a proton.

[00:20:19]Let's talk about those isotopes. Each element has many different forms. For each specific element, the number of protons in the nucleus is the same, 11 protons for sodium, but there can be different numbers of neutrons in the nucleus. All these different forms are called isotopes. They're chemically identical to each other, but with slightly different masses. The number you see next to the chemical symbol is the total number of protons and neutrons in the nucleus. There are 21 known isotopes of sodium, and of these 21, there is only one stable, non-radioactive isotope, sodium 23.

[00:21:07]Sodium is therefore a mono-isotopic element.

[00:21:11]Because of this, sodium 23 makes up 100% of what we see in nature.

[00:21:17]By the way, the word isotope comes from the Greek isos, meaning same or equal, and topos, meaning place. I assume you've used a topographic map to find your place and altitude.

[00:21:33]All these various isotopes of sodium occupy the same place in the periodic table.

[00:21:42]Of the radioactive isotopes of sodium, these are the longest-lived, the ones with half-lives over 1 second. They're all pretty short. More on half-life in the next slide. The longest sodium half-life is sodium 22 with a half-life of only 2.6019 years. That's known pretty accurately.

[00:22:05]So, you're unlikely to encounter any of the radioactive isotopes of sodium. Any radioactive isotope of sodium out in nature has long ago decayed away, given the 4.5 billion-year age of the solar system.

[00:22:22]What's a half-life? This graph shows an exponential decreasing curve. As an example, let's say we start with 1,024 atoms of any radioactive isotope. It doesn't matter which. I chose 1,024 atoms because it's a power of two and we'll be doing a lot of divisions by two.

[00:22:43]If we wait one half-life, one half of our isotope will decay and we'll have 512 atoms left. If we wait one more half-life, half of that half will decay, leaving us with one quarter of the original 1,024, or 256 atoms.

[00:23:04]Another half-life, half again as many, or 128 atoms, and so on. Just keep dividing by two every half-life. After 10 half-lives, we'll have about 1/1000 of our original amount.

[00:23:22]By the way, notice that there's one remaining atom after 10 half-lives. If we waited one more half-life, our remaining atom would have a 50/50 chance of decaying in that time.

[00:23:37]Here's the periodic table of the spectra. If you excite atoms, they give off specific colors of light, and this is the spectrum of sodium atoms. Though there are many colors, what stands out are two very closely spaced yellow colors that are many times brighter than all the others, much brighter than you're seeing here.

[00:24:00]Spectra of the elements uniquely identifies them to scientists as each gives off its own unique set of colors.

[00:24:08]Spectroscopy is one of the most powerful tools of science.

[00:24:14]Joseph von Fraunhofer looked at the spectrum of the sun.

[00:24:19]This is a bit different than the spectrum in the previous slide. Here, white light with all the colors from the lower layers of the sun's atmosphere shines through cooler outer layers.

[00:24:32]The elements in these cooler outer layers absorb specific colors of light just as they would emit if excited.

[00:24:41]This results in an absorption spectrum.

[00:24:45]Fraunhofer labeled these lines from A to K, and I want to draw your attention to the D lines. These are the lines from sodium in the atmosphere of the sun.

[00:24:59]Other lines are from other elements.

[00:25:02]Using modern instruments like this one at Kitt Peak Observatory near Tucson, Arizona, we can measure the spectrum of the sun very accurately. This should be in a single strip, but for the sake of visibility, that strip has been sliced and stacked to fit everything in one graphic. Here are the sodium absorption lines. They're only about half of a nanometer apart in wavelength.

[00:25:29]That's actually really close, but this is a very spread-out spectrum.

[00:25:34]Here are the three lines from hydrogen in the visible spectrum, H alpha, beta, and gamma.

[00:25:43]Every dark line you see here is associated with some element in the outer, cooler layers of the sun's atmosphere, and I've labeled a few more.

[00:25:53]Notice there are lots of iron lines. It has a very complicated spectrum. I apologize for the small size of the labels. Pause the video if you want to take a closer look.

[00:26:07]You can see the brilliant yellow color of sodium by mixing a bit of table salt in some alcohol and setting it on fire.

[00:26:15]Be careful if you try this. It might be smart to have a fire extinguisher I was using a very small amount of alcohol, only about 1 cc. Just for fun, this is the flame with boron. Boric acid is what I added to the alcohol. And here's what you get when you add lithium chloride to the alcohol. These are a few of the chemicals used to make fireworks show all those spectacular colors.

[00:26:45]Unlike our previous element, neon, sodium just loves to participate in chemical reactions and is part of many chemical compounds. Let's take a look.

[00:26:58]This is a low-pressure sodium lamp. The U-shaped tube inside is evacuated to about 1/100,000 of an atmosphere, and a small piece of sodium is placed inside. Since sodium is a solid at room temperature, some argon and neon are also included in the tube to vaporize the sodium on startup.

[00:27:23]Here's what it looks like as the lamp warms up. You first see only neon and argon glowing, like at the very top, until the sodium begins to vaporize.

[00:27:34]Notice it takes 3 minutes to reach operating brightness, one reason this lamp is unsuitable for many uses.

[00:27:43]Once warmed up, the tube glows a brilliant yellow. This is a very efficient lamp, converting around 30% of the input power into visible light.

[00:27:54]White LEDs convert about 25%.

[00:27:57]Fluorescent tubes convert up to 15%, and ordinary incandescent lamps are only 2.5% efficient. Here I've listed the efficiencies as lumens per watt.

[00:28:11]This is how much light they make for each watt of power you put in.

[00:28:16]As efficient as they are, low-pressure sodium lamps have one huge problem. They only emit a very narrow yellow color of light, so they're unsuited for most lighting situations.

[00:28:31]This room, the monochromatic room, is lit only with low-pressure sodium.

[00:28:38]Inside this is a painted bench that looks rather dull. Only yellow light of various brightnesses reflects from it.

[00:28:47]When illuminated with white light, an entirely different picture emerges.

[00:28:53]Likewise, your Crayola box of 64 colors is underwhelming until white light reveals the true nature of their colors.

[00:29:03]This is a high-pressure sodium lamp. By high pressure, I mean this lamp is at a pressure of 1/3 of an atmosphere, compared to the 1/100,000 atmosphere for the low-pressure sodium lamp. This lamp has a completely different look. Its light is still yellowish, but also contains other colors, so it looks more of a pale yellow.

[00:29:28]You still wouldn't want to use this in your house, but they have been extensively used in street lighting.

[00:29:35]They're now being replaced by cheaper, whiter, and more efficient LED lighting.

[00:29:42]Here's the spectra of high-pressure sodium light on the top and low-pressure sodium on the bottom. Note the low-pressure sodium only puts out a single yellow color. While the high-pressure sodium lamp has a much broader spectrum and even a dark absorption line where the low-pressure sodium emits its light.

[00:30:08]Sodium appears in thousands of chemicals. I couldn't possibly cover them all, but these are a few you might be familiar with.

[00:30:17]Sodium chloride has a simple molecule of one sodium and one chlorine atom. You're [snorts] familiar with this as common table salt. This is a photo I took through a microscope. You can see the cubic crystalline structure. The cubes are slightly rounded from all the abrasion in the salt shaker. Sodium is an essential element to our biology.

[00:30:39]Sometimes we have to supplement livestock by giving them a huge block of salt for them to lick. Uh appropriately called a salt lick. Despite its solubility, salt occurs in nature as halite in evaporating salt ponds. Here it's seen in combination with another evaporite, borax, which we'll get to in a moment. You can even purchase lamps made from Himalayan sea salt.

[00:31:08]Sodium hydroxide, also called caustic soda or lye, is a strong alkali. You may be familiar with it as crystal Drano, which was invented in 1923 by Harry Drackett. For years Drackett advertised once a week Drano in every drain. He was responsible for many other household products like Windex for instance.

[00:31:36]I want to make a quick side trip here.

[00:31:39]Sodium hydroxide, which we saw on the previous slide is an important part in making soap from oil or triglycerides by a process called saponification.

[00:31:52]You start with some form of oil such as palm oil and add sodium hydroxide and heat.

[00:32:02]This breaks the hydrocarbon head from the hydrocarbon strings and hydroxyl ions from the sodium hydroxide join this to form glycerin.

[00:32:13]Meanwhile, the long hydrocarbon chains which have a negative charge on their oxygen ends find and pick up sodium ions charged positively also from the sodium hydroxide forming a fatty acid salt, which is soap. This may be in the form of sodium oleate or sodium stearate.

[00:32:37]This is something you can try at home as long as you're careful with the caustic sodium hydroxide. Always wear gloves and eye protection and probably old clothing if you're smart.

[00:32:49]There are many YouTube videos showing this process.

[00:32:55]Sodium tetraborate decahydrate or more simply borax occurs naturally and is used commonly as a laundry detergent booster, multi-purpose cleaner, deodorizer and insecticide.

[00:33:09]Large deposits are found in Nevada and Death Valley.

[00:33:13]The famous brand here, 20 Mule Team, celebrates the only way to haul out the mineral the 165 miles from Death Valley for processing. Yep, that's why it's 20 Mule Team Borax.

[00:33:27]A bit of a misrepresentation actually.

[00:33:29]It was really 18 mules led by two horses.

[00:33:35]Sodium carbonate can be used for water softening and detergent production, but its primary use is in the production of soda lime glass.

[00:33:46]This is the most common affordable type of glass making up around 90% of global glass production for windows, bottles and jars. It's made of silica, sand, sodium carbonate, soda, and calcium oxide, lime. It's highly workable, chemically stable and recyclable.

[00:34:09]Soda lime glass's only problem is it has low thermal shock resistance and must be tempered to increase strength.

[00:34:19]Sodium nitrate is a widely used chemical for fertilizer and food preservation.

[00:34:24]Like its cousin potassium nitrate or saltpeter, sodium nitrate can also be used as an oxidizer in pyrotechnics and explosives. Most people are familiar with it as a preservative and color fixative to cure meats and poultry such as hot dogs, ham, bologna. Yes, that's how it's pronounced in the United States. Please no comments. And bacon.

[00:34:48]Mm, bacon.

[00:34:51]It's worth mentioning a very closely related chemical to sodium nitrate, NaNO3, is sodium nitrite, NaNO2, differing by a single oxygen atom.

[00:35:04]Sodium nitrite is used along with sodium nitrate to speed up the curing of meat, inhibit bacterial growth, increasing the shelf life and through reactions with myoglobin in the meat impart reddish and pinkish colors. Though there are positive aspects to these as food additives, there's some evidence there may be a very small risk for certain types of cancer.

[00:35:31]That said, I'll take a small risk over the much larger risk of sickness by botulism or other food-borne bacteria.

[00:35:39]Again, please no comments. It's a matter of risk management.

[00:35:44]Even though it's not on my list, another preservative, sodium benzoate, used in many foods is also worth a mention. It's mostly used in acidic foods, vinegar-based dressings, sodas, jams and jellies, fruit juices, pickles and others.

[00:36:01]Sodium acetate has many uses in the biotech, industrial and food industries, but most people have probably encountered it in reusable hand warmers.

[00:36:12]It's often called hot ice.

[00:36:16]Inside the sealed container is a super-saturated solution of sodium acetate in water. A small metallic clicker button is snapped to initiate crystallization.

[00:36:27]The rapid crystallization is exothermic and releases substantial heat.

[00:36:33]To recycle, you boil the packet to redissolve the crystals and it's ready for another warming cycle.

[00:36:42]Almost everyone's familiar with sodium bicarbonate. In a short list of ingredients, combine it with a bit of aspirin and a bit of dry citric acid for the fizz and you have the ingredients of antacid Alka-Seltzer. Without all those extra ingredients, you can get pure sodium bicarbonate at the grocery store as good old baking soda. Baking soda has many uses such as a leavening agent, a deodorizer, a mild abrasive for cleaning and of course one of the main ingredients you need to make that vinegar baking soda volcano seen in every science fair.

[00:37:23]Lastly, sodium thiosulfate is used in the last step of developing film and prints. Well, before we had digital cameras.

[00:37:32]The sodium thiosulfate dissolves out the remaining undeveloped silver nitrate from the film emulsion preventing the photograph or negative from fogging or darkening later with exposure to light.

[00:37:45]Sodium thiosulfate is also a dechlorination agent for water treatment in swimming pools and can be used for treating cases of cyanide poisoning, though there are better modern alternatives.

[00:37:59]When you add salt or sodium chloride to water, it lowers the freezing point. As we all remember, pure water freezes at 0° C or 32° F.

[00:38:11]Adding salt to make a brine lowers the freezing point to about -18° C or 0° F.

[00:38:20]And indeed, this is what Daniel Fahrenheit based his temperature scale on. 0° F was the coldest temperature he could make. He was trying to avoid negative temperatures. Celsius was not so concerned with negative numbers. So, why is this important? Well, if you're trying to keep a road ice-free and the outside temperature is above -18° C or 0° F, you can simply apply brine to the road.

[00:38:54]Deicing roads and airplanes involves using salts such as sodium chloride.

[00:39:00]Similar salts are also used such as magnesium chloride and calcium chloride, which work at even lower temperatures.

[00:39:08]Of course, they all have environmental issues when they run off as warmer weather and rains wash them away.

[00:39:17]Sodium has some real advantages if used as a reactor coolant. Sodium melts at 98° C and boils at 883° C.

[00:39:29]It's liquid in a 785° C range.

[00:39:33]Water only has a 100° C liquid range.

[00:39:39]Heat-wise, while water can absorb three times the energy than sodium to raise its temperature by 1°.

[00:39:46]The liquid range of sodium is larger by a factor of almost eight, more than making up for the difference.

[00:39:54]A sodium-cooled reactor does not need to be pressurized like a water-cooled reactor, reducing the possibility of leaks and allowing much lighter and thinner materials for the system's structures.

[00:40:08]Sodium conducts heat about 150 times better than water and is a good electrical conductor, so it can be pumped electromagnetically with pumps containing no moving parts.

[00:40:23]Sodium does not corrode metal parts of the reactor like water and because it does not slow down neutrons in the core as much, produces reactions that create far less radioactive waste.

[00:40:37]The disadvantage is that you're dealing with hot liquid sodium, which if it does leak, bursts into flame if oxygen is present. Running in a nitrogen-only environment would prevent this.

[00:40:50]Also, the reactor makes all the sodium radioactive, but it's short half-life of only 15 hours kind of renders this a non-problem.

[00:41:00]Though there have been many sodium-cooled low-power research reactors built, actual power-generating commercial reactors are running in China, Russia, and India. Prototypes by TerraPower are currently in early construction stages in the US and look very promising.

[00:41:24]Speaking of energy generation and specifically energy storage, an invention that's been in the works for quite a while is the sodium-ion battery.

[00:41:33]You are no doubt familiar with lithium-ion batteries, which power just about everything nowadays. The problem with lithium is it's fairly rare, expensive, and has environmental costs associated with its extraction.

[00:41:47]Lithium-ion cells also use some relatively rare metals, cobalt, copper, and nickel. Sodium, on the other hand, is very common. Think salt water and does not require rare metals.

[00:42:02]While sodium-ion batteries don't quite have the same energy density as lithium-ion, they have better low-temperature performance, faster charging times, more charge-discharge cycles, hence longer life, and less chance of thermal runaway issues. Also, because of the materials, they should be less expensive. Only recently has it become practical to manufacture these at commercial scale. So, I think we'll be seeing more and more of this technology for electrical grid storage and EV usage in the near future.

[00:42:37]Like all YouTubers, I've saved the best for last. You want to see sodium thrown into water.

[00:42:43]Well, first, let's look at the chemistry behind that reaction.

[00:42:49]So, two atoms of sodium react with two molecules of water, producing two molecules of sodium hydroxide and a molecule of hydrogen.

[00:43:04]This hydrogen is important, as we'll see.

[00:43:08]So, here is that reaction with a small piece of sodium you can see on the dinner plate.

[00:43:15]So, what I'm going to do is get my chopsticks.

[00:43:18]And I'm going to pick that up.

[00:43:22]And I'm going to just put a little splash shield up here. I'm going to drop this into the water, so we'll wait for Chuck.

[00:43:30]Sorry, go ahead. So, here we go. We're going to now drop the I'm going to drop this little piece of sodium into the water and we'll see how it reacts. Here we go.

[00:43:44]So, it's kind of skittering around on the surface there. I think it's hot enough.

[00:43:48]There it goes.

[00:43:51]And that's why we put the splash shield on the top.

[00:43:55]Perhaps I should have warned the camera person about the small hydrogen explosion.

[00:44:02]Theodore Gray likes to use somewhat larger chunks of sodium at his parties.

[00:44:07]Notice the brilliant yellow color of the sodium flame.

[00:44:19]And of course, the military, after World War II, needed to dispose of huge quantities of sodium and managed to find the most unenvironmental way to accomplish that task.

[00:44:35]>> [music] >> 20,000 lb of highly dangerous metallic sodium head for destruction in Lake Lenore, Washington. The government surplus chemical ignites and explodes [music] when wet. The alkali lake is devoid of fish and forms an admirable disposal spot. A 3,500-lb container of sodium hurtles into the lake [music] and crashes through a foot of ice. As the water seeps in, smoke rises through a series of muffled explosions.

[00:44:59]>> [music] [music] >> The acrid clouds billow several thousand feet over the steep sides of the lake.

[00:45:13]Disposal of the chemical by the War Assets Administration is made necessary because no public carrier will accept it for transportation to a purchaser.

[00:45:21]One after another, with varying effects, the containers go up with spectacular results as water and sodium meet.

[00:45:30]>> [music] >> A ONCE-LETHAL WAR chemical becomes a peacetime pyrotechnic display.

[00:45:40]Times were different back then.

[00:45:43]The solution to pollution was dilution.

[00:45:47]You have about 90 to 100 g of sodium in your body. That would be a cube about 4.6 cm across, a little over 2 in, quite a bit.

[00:45:59]Of course, in your body, this isn't in the form of sodium metal, but rather chemicals containing sodium. About 1/2 is in your bones and the other half is in your vital bodily fluids and tissues.

[00:46:13]That's why you're salty.

[00:46:15]Sodium is an essential electrolyte, crucial for maintaining fluid balance and blood pressure regulation.

[00:46:23]Proper sodium levels are vital for heart health and especially nerve signal transmission.

[00:46:30]Overconsumption, mainly as salt, can lead to high blood pressure. You only need about 1/2 of a gram every day to function.

[00:46:39]As usual with my element talks, we'll end with Mary Soon Lee's elemental haiku about sodium's importance in nerve signal transmission.

[00:46:51]Racing to trigger every kiss, every kind act, behind every thought.

[00:47:01]In the next program in this series, we'll check out a very light metal you may have encountered in its elemental state, magnesium. I hope you'll join me.

[00:47:12]I'm your host, Ron Hipchman. Thank you for watching this Tales from the Periodic Table program about the element sodium.

[00:47:23]For more Tales from the Periodic Table, see this playlist on my YouTube channel.

[00:47:28]And of course, I'm required by law to say this, smash that subscribe button.

[00:47:37]>> [music]