Physical properties of elements on the periodic table

0:00- [Instructor] Take a moment and look around you, what do you see? You might see a shiny spoon, or a dull basketball. You might see a soft pillow, or a hard wooden table. You might see certain things that are solids, like your computer, or liquids, like the water in your water bottle.

0:15They all seem so different, but here's the fascinating part even though the world seems filled with endless variety, everything around us is made from different combinations of just 118 building blocks, that's it. These are called the elements. So let's explore these elements in detail.

0:38So what's an element? An element is a pure substance made of only one type of atom throughout. It cannot be further broken down into simpler substances. And you're probably familiar with a few. You've probably heard of gold, silver, copper, aluminum, oxygen, all those are elements.

0:56So why is gold an element? Well, because gold is only made of gold atoms and nothing else. Silver is an element because it's only made of silver atoms. Copper is an element because it's only made of copper atoms. In contrast, if you consider stuff, like water or steel, they are not elements because they're not only made of one kind of atoms.

1:15For example, water is made of two kinds of atoms, oxygen and hydrogen. Steel, for example, is also made of two kinds of atoms, iron and carbon. And similarly, most things around us, like the shirt that you're wearing or the plastic water bottle in which the water is, all those things are made from multiple elements, a combination of multiple elements.

1:34So in chemistry, we often begin by studying the simplest substances first, the elements, because once you understand these building blocks, it becomes much easier to understand the more complicated materials built from them. So how do we study these elements? Well, we can study their physical properties.

1:53Think of physical properties as observable features. You've likely heard of some, like their mass, volume, density, which state of matter, whether they're magnetic or not? Do they dissolve in water? Do they conduct heat or electricity? All these are physical properties.

2:11But let's also talk about some other physical properties that you may not have heard of, but they're very useful for us, for example, luster. It, you know, tells us whether something is shiny or not. Can it reflect light or not? For example, gold is pretty lustrous because it's pretty shiny.

2:27But charcoal, which is basically carbon, is not shiny. So it doesn't have luster or we say it's not lustrous. Okay, another one is malleability. It tells us whether something can be hammered into thin sheets, whether something is bendable. Again, if you look at gold, you can hammer into thin sheets, so it is malleable, but if you take charcoal, it's not.

2:50If you try to hammer it, it'll just break. So charcoal for example, is not malleable. Another one is ductility, it tells us whether something can be shaped into a wire. For example, copper is very ductile because you can make wires out of it. But charcoal, again, is not ductile.

3:11You can't make wires out of charcoal. And then there's an important one, fluorescence if it can glow or emit light immediately after absorbing light. A good example of this is your highlighter ink. If you turn on your backlight or UV light, you'll see it glows under that, we call that fluorescence.

3:33Now, this looks very similar to the glow in the dark stickers that was there in my room. When I was a kid, not now, but they're not the same thing, there's a difference. See, over here, even after you switch off light, the stickers glow, right, the glow persists.

3:49But in fluorescence, that doesn't happen. The moment you switch off the back light, the glow is gone. You switch on the backlight again, it glows, so it happens immediately and it loses that glow immediately once you turn it back off. But glow in the dark stickers are not like that.

4:05Even when you turn off the light, they are still glowing. That's why it's called glow in the dark. This, by the way, is called phosphorescence. And both of these are different from another kind of glow that you may have seen in your glow sticks, for example. That's called came chemiluminescence.

4:20Here, the glow happens due to chemical reactions. So this is a chemical property, not a physical property, okay? So these properties are very useful because it can help us predict stuff. It can also help us decide what materials we should be using given our use case.

4:35For example, if you wanna conduct a scientific experiment where we need a very thin sheet, well, we will use gold because it's highly malleable. If we want wires to conduct electricity, let's choose something that can be ductile and conducts electricity. Copper is a good example of that.

4:51Okay, so now what we can do is go back to those 118 building blocks, the elements, and categorize them based on their physical properties. But 118 is a lot to remember and categorize. So we like to organize all those 118 elements into three general categories based on the similarities that we observe.

5:13These three categories are: metals, metalloids, and non metals. So let's check some examples. You've probably heard of metals: gold, silver, copper, aluminum, so on. Metalloids include silicon, germanium, yes, used in your computer chips. And non metals are oxygen, carbon, sulfur, and so on.

5:33All metals have similar properties, which are different from, say, non metals. Okay, how are they different? Let's see, let's start with the state of matter. What state of matter they are at room temperature. You'll find that metals are mostly solid. I say mostly because there are exceptions.

5:51For example, mercury is a metal, but it's liquid at room temperature. And what about metalloids? They're also solids, but non metals, they're mostly gases and solids. But again, there's an exception over here. Bromine is a liquid non metal, and this will be the theme.

6:09Whatever we're talking about is a general trend, but there will always be exceptions, remember that. Okay next, let's talk about their density. Metals are usually more dense than water. What about non metals? Well, if you consider gases then, they are less dense than water.

6:25And if you consider the solid non metals, they are more dense than water. What about metalloids? They are less dense than metals, but they're usually more dense than non metals. And so you can, you can sort of see that metalloids have properties that are in between that of metals and non metals, okay?

6:43What about magnetism? Well, some metals are magnetic, like iron, nickel, cobalt, but metalloids and non metals, they're mostly non-magnetic. Okay, let's talk about luster. We've already seen this, metals are pretty shiny. Non metals are pretty dull. Metalloids, well, most of them are shiny.

7:01Malleability, metals are highly malleable, but these two are not. Ductility, metals are pretty ductile, these two are not. Okay, what about electric and heat conductivity? Metal, great conductors, non metal, bad conductors, metalloids in between so we call them semiconductors.

7:19And that's the primary reason metalloids like silicone, for example, are used in building computer chips because of their semi-conductivity. Okay, what about fluorescence? Well, most metalloids and non metals are not fluorescent at all. What about metals? Well, there's a particular class of metals that are highly fluorescent.

7:35We call them rare earth metals. Now, despite their name, they're actually not very rare. They're called rare because they are usually spread out and they're not clumped together like, you know, iron, for example, or gold, for example so it's harder to obtain in larger amounts, it's hard to purify.

7:54And these metals are extremely important in modern technology. Think about electric vehicles, wind turbines, smartphones, televisions, they're used in all those things. And since these are metals, they share the same properties as metals, but they also have some very unusual properties.

8:10For example, if you consider europium, it is highly fluorescent and therefore, they're used in fluorescent lamps. Neodymium, for example, is highly magnetic. And so they are used in making powerful magnets. For example, the ones that you find in your earbuds. Okay, so how do scientists organize these 118 elements into metals, metalloids, and non metals?

8:31Well, they do that inside one of the most famous charts in science, the periodic table of elements. This table organizes all known elements in a very useful way. First of all, each element has its own ID and a symbol. H for hydrogen and that's number 1. Then comes helium, which is at number 2, and so on, and so forth.

8:52And the last element is 118, oganesson. Okay, what about these elements that are down over here? Well, they're actually located over here, but that would make the periodic table much wider. So to make it a little bit more concise, we keep them down below and we add the indicators here.

9:08Okay, but the most important thing is that the position of an element on a table tells us important information about its properties, what exactly? Well, you can see most elements over here are metals, and these are the rare earth metals. And they are found mostly on the left side and the center of the table.

9:31And you can see the non metals are mostly on the upper right side of the table, and the metalloids are in between. They often form a stair step pattern between the two groups, which makes sense because their properties are also in between these two. So look, the word periodic means repeating.

9:50Just like the patterns repeat in a calendar, certain patterns also repeat across the periodic table. For example, along a particular row, you go from metals to metalloids to non metals. And then repeat metals to metalloids to non metals, and so on. And if you look at the elements along a column, then they have very similar properties.

10:10So if you look at these six elements, they're all metals, but these three, very similar properties. These three, very similar properties. Similarly, all these six elements are non metals, but these three, very similar properties. These three, very similar properties.

10:27Lastly, even though there are 118 elements, most of the universe is made of just two of them, hydrogen and helium, and traces of oxygen as well. In fact, hydrogen and helium together make up about 98% of the universe. Okay, but what about our Earth? What is it primarily made of?

10:47Well, that depends on what you're looking at. If you consider the atmosphere then, it's mostly made of nitrogen and oxygen. On the other hand, if you're looking at the oceans, it's mostly made of oxygen and hydrogen because water is mostly made from those two elements.

11:02What about Earth's crust? Well, it's made of large amounts of oxygen, silicon, and then you also find traces of other elements like these. But what if you consider the entire Earth as a whole, what it's made of? Well, it's mostly made of iron because there's a lot of ion in the Earth's core.

11:18And finally, what about us, what are we mostly made of? We are mostly made of oxygen, carbon, and hydrogen. So, to sum up, physical properties help us identify and describe different kinds of elements. If you know the properties of a substance, we can make predictions about what kind of elements it may contain, what elements should we be using based on our use case.

11:37And if we know where an element is located on a periodic table, we can predict some of its properties, whether it's a metal, or a non metal, and so on. Chemistry is really about discovering patterns in the materials that make up our universe. And as we begin learning these patterns, we start to understand the world around us in a completely new way.