lecture 5.4 and we're going to start looking at the periodic table a little more closely in this lecture early on this would be what your periodic table would have looked like which doesn't look a lot like what we have today but Mendeleev was the first to create and publish a periodic table and this was done in 1872 And you can still see, however, that the groupings, so this is group, same as our group one, and you'll notice it has lithium and potassium and rubidium and cesium. So the same elements grouping them together, and same thing, there's some differences, of course, but they had the right idea all the way back in the late 1800s of how they wanted to group the periodic table. The periodic table basically will always list all the known elements and it indicates the position of some man-made elements.
So if we extend our number of elements by doing some fancy physical combinations, in other words, we have the ability to basically slam protons and neutrons into... other elements and increase the number of protons. These are man-made elements.
They basically smash element nuclei together inside of these nuclear reactors and they can create new elements. They don't tend to be terribly stable, which is probably why they don't exist in nature, but we do have the ability at this point to create new elements. All right.
And as you see down here, these guys in gray, these are not naturally occurring elements. These are elements that we have created. And some of these, these are the unknowns over here where we've added places to put even more of these man-made elements.
And so... If you go on in chemistry and become part of the nuclear group, you might even be able to put your name on a new element if you can create it. But this is the periodic table, and as you can see, the information that you can get in the periodic table is the element symbol, hydrogen over here, the element's atomic mass and atomic mass units, the atomic number, which indicates, again, the number of protons, right? We remember that. And of course that's what makes each element individual.
In this particular periodic table, you can see that the solids, the liquids, and the gases are defined. I don't know if the color is a little bit hard, but most of your periodic table are solids. And the reds? Over here are gases and there are a limited number of those and you should know them.
Most of them are the noble gases, but nitrogen, oxygen, chlorine, and hydrogen are also gases. You have two liquids, which are bromine and mercury. They're in blue, which is hard to see on this periodic table, but you should know what the liquids are.
You should know what the gases are, and then everything else is going to be a solid. And so this is exactly what I just showed on the previous periodic table. You should know your gases, and you definitely should know that bromine and mercury are the only two liquids. Okay?
In the periodic table, the reason we call the periodic table a periodic table is because that the rows, that's the horizontal. rows in the periodic table are actually called periods. And they're separated by the way electrons surround the nucleus and you'll learn this very well later in the semester.
And any of these, and you know this already, we call these groups. So the columns are called groups and the rows are called periods. Now let's talk a little bit about each of the groups in the periodic table.
The first group is called the alkali metals. And the alkali metals are soft metals, so they're not what you would normally think of as a metal like iron or copper, which are nice and hard, dense metals that they bend, but they're very difficult. When you look at something like the alkali metals, they almost have the consistency of like a...
heavy cheese you can actually cut them with a knife and they are also extremely reactive in water This is a very what we call exothermic reaction because when it reacts with water it gives off a lot of energy in the form of heat and Of course that heat can ignite the oxygen in the air and that's why we see the flame here. So This is very very reactive metals the alkali metals. Group T2 sorry is called the alkaline earth metals and this is also because they are very reactive with water but they form something called a hydroxide base and an alkali you know we call alkali is base so if you have something that is a base in water or basic we say it's alkaline and this is where the name for the alkaline earth metals comes from they are also softer than most and they have the lower densities than most other elements or metals I should say but not quite as soft or as reactive as the alkali metals now we get into groups through 12 which are the guys in the middle there and those are called the transition metals and so they are more traditional metals these are the ones like copper and iron and zinc and so forth where they're hard they're dense and you can you can shape them but they don't react as well in terms of like the alkaline earth metals alkaline metals so they're not going to create sort of an explosion or a very high heat when they're placed into water.
But the nice thing about them is if you put them in solution, they often combine with water to create really pretty colors. So copper turns the solution blue, nickel green, cobalt makes it red. Chromium has several different colors that it can form depending on how basic the solution is, so if it has hydroxide or ammonia, and so you get different colors. So the transition metals are harder and more dense, and they create pretty colors when they're placed in solution.
Now the next group over, starting at group 13 and running sort of across here on this diagonal, is something called the metalloids. and they're called metalloids because they are similar to metals in some ways but they're also similar to non-metals in some ways and so if we talk about metalloids we're talking about a line between the metals which are on this side and the non-metals which are over here in the periodic table and so this is sort of a fence between And as you can see, there are several different properties here. They can act as semiconductors, meaning that they are a little bit in terms of electrical conductivity. In other words, they can conduct electricity at high temperatures but not at low temperatures. So this gives us some control on whether or not we want electricity running through.
the metal. So if you have high temperatures basically the metalloids act like metals. At low temperatures they act like nonmetals.
And so we can use this in electronic devices. So just something to think about. Now this is group 15 which is named for the nitrogen being at the top. And If you've ever looked at certain types of gas suppressions, sorry, fire suppression systems, they contain a lot of nitrogen, and that's because nitrogen has the ability to essentially stop fire, so it chokes it off, and that's where the name for the group comes from. It's called a nictogen, so if you can kind of see it sort of sounds like nitrogen, but it's called a nictogen.
And the nictogen group is the nitrogen group, group 15, and it comes from this word choke in Greek. And so all of the nitrogen group is grouped together also because of their electron configuration. But we'll talk about that later. Group 16, and this is called the chalcogen group. All these groups have different names based on Greek origin words.
And the Chalcogen group contains both oxygen and sulfur. And this is because both of these are found in ores, and ores are just basically metals that combine with oxygen and sulfur. And so they named the group Chalco, so Chalcogen, because Chalco means ore. and gen means formation so they are present, oxygen and sulfur are commonly found in the different metal ores that we have in the ground. So we'll continue on with this. 17, you've probably heard this before, is called the halogen group and that's the fluorine, chlorine, bromine, iodine group.
They are all diatomic. Remember we talked about being diatomic elements, so all the halogens are diatomic, and they form a lot of salts. We see halogen salts quite a bit in chemistry, so you'll become very familiar with the halogens.
And then group 18 is called the noble gas group, and the reason they are considered noble is they don't play well with others. We'll talk about why later, but they don't form ions. They're all odorless and colorless, and they're pretty inert, meaning that they don't really do a lot with terms of reactivity.
They don't form reactions very often because they don't need to. And again, we'll explain why later, but this is the noble gases in group 18. So we... have kinda gone through the groups right so alkali metals alkaline earth metals transition metals we go to the chalcogens this group this one here nictogens sorry I did that backwards nictogens has a special name chalcogens halogens and then of course the noble gases so we've gone through all of these that have special names the values right along here, that's where those metalloids are. And so you should be able to do that.
You should be able to go in and name each of these groups in the periodic table. You should also know that the group over this side are metals, and that on the other side of the metalloid line, these are nonmetals. You need to know that because that'll tell you whether or not you're making a covalent or an ionic compound. So there are reasons to know where everything is located in the periodic table. Now there's two rows that we haven't talked about yet, and these are called the lanthanides and the actinides, and they're combined called the rare earth elements.
And that's because they're not very common. In other words, they're not found in high amounts. You can think of, you know, we talk about uranium. It's one of the actinides. And, of course, it's not a very common metal.
We don't find a lot of it, which makes it very precious. And also, a lot of these metals are radioactive. Okay? So you find a lot of the radioactive metals in these two groups. Okay?
All right. So. You need to know, as I said, these segments in the periodic table.
So all of the blue, these are your nonmetals. We need to know those, right? The metalloids is that sort of fence between the metals and the nonmetals. And then of course everything in red is metals.
And again, you should spend some time, make sure you can identify these because they do help you determine whether or not you're working, you know, metal plus non-metal is an ionic compound, two non-metals is a covalent compound. The other thing that you have to know from the periodic table, and this is because I'm a mean old professor and I think you can't really speak chemistry unless you know the alphabet, is you should know the first 56 elements in the periodic table plus these because these are commonly used in commonly known so you need to know their names and their symbols no you do not need do not know need to know the mass ok so you don't need to memorize any numbers although if you do enough practice you'll probably memorize some of the masses but You don't need to know the numbers. I just want you to know the names and the symbols and be able to spell them.
You know, spelling counts. And I keep misspelling things all the time. So spelling does count.