Ch.2 - Atoms & ElementsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Ever wonder where did this periodic table ever come from? At the end of the 18th century, Lavoisier compiled a list of the 23 elements known at the time. In 1869, Dmitri Mendeleev coined the term "Periodic Table".

Group Names and Classifications

Concept #1: Classification of Elements in the Periodic Table 

Transcript

Ever wonder where exactly did the periodic table come from? Well, we can thank the French nobleman Lavoisier. He was the one who basically is known as the 'Father of Modern Chemistry.' He basically helped to predict the names of oxygen and hydrogen and successfully predicted the element silicon. He was great when it came to studying patterns in chemistry as well as biology. And, it’s because of him, they were able to construct a list of the first 23 elements that would eventually lead to the periodic table.
Now, it wasn’t until 1869, when we had Mendeleev who used the word periodic table for the first time. He saw patterns in these elements. He saw that they increased in mass over time. And then, he saw that their electrons arranged themselves in certain patterns, which caused them to have similar chemical properties.
We’ll get more into this type of periodic law, as well as electrons later on in the semester. But, just realize, it’s because of these two great scientists that we have the periodic table. Today, we have well over 110 elements in the periodic table, 114 and counting. We’re going to say that a majority of them occur naturally in our environment and there are some that we’ve even synthesized in the laboratories.
Now, if we take a look at the periodic table, you’re going to have to realize that when it comes to the periodic table, you’re going to have to memorize a few of these elements. Most professors will want you to memorize the first 30 elements. But, honestly, to be entirely safe, I would recommend memorizing elements 1 to 36.
Now, when I say memorize, I don’t mean memorize the symbol and all the numbers associated with it. That will come over time through practice and problems. When I say by memorize, I mean realize that when I see Ni, what element is that? That’s nickel. This would be titanium, magnesium. Memorizing the first 36 symbols will help you in a long way to figure out what exact element are we talking about when you’re given a symbol.
Now, we have to realize that the periodic table, because of the periodic law given to us by Mendeleev, is set up this way because it follows their reactivity in chemical properties. We don’t need to know exactly what those are yet, but just realize that the periodic table is set up this way for a very good reason because this is the way their electrons arranged themselves.
But, what we need to know right now is exactly, what do certain areas of the periodic table tell us. Now, what we should realize is that there are basically three types of groups in the periodic table. There are metals, there are metalloids, and then there are non-metals.
Now, here when we go to B, B is called boron. And, what we’re going to do here is we’re going to draw a staircase. Here goes our staircase. Now, we’re going to say on this staircase, there’s boron, there’s the silicon, there’s arsenic, there's Te and At, these five elements that are on the staircase. Right underneath the staircase are these two: germanium and antimony (Sb).
These seven elements that I’ve highlighted with these blue streaks, these are our metalloids. Metalloids are called semiconductors. What exactly does that mean? Well, semiconductors means that they conduct electricity. You can run electricity through them. Not as well as metals, but much better than non-metals.
Metalloids are basically a blending of non-metals and metals. They don’t exactly fit in metal category or non-metal category. What they are, are kind of like a hybrid of the two. Metalloids are really important in industry. Like, the computer chips that we have in our cellphones, in our computers, in our TVs—they come from certain types of metalloids. They come from silicones. Silicon chips that are in those structures, those are metalloids.
Now, those seven are metalloids. We’re going to say everything here in red to the right of it, so all these guys here, all of these guys are our non-metals. We’re also going to say hydrogen over here, even though it’s over here. It’s also a non-metal. The ones in the blue streaks are your metalloids. The ones that are in red are your non-metals.
Non-metals tend to be brittle and dull in color. They don’t conduct electricity. They don’t insulate. They don’t hold on to heat very well. These are the properties of non-metals. We’re also going to say that it seems like there’s a lot fewer non-metals because everything else that’s not with blue streaks or not in red is considered a metal.
As you can see there’s a lot more metals in the periodic table than anything else. Metals tend to be shiny. They conduct electricity very well. These are the properties that we’ll see with metals. They’re very reflective. Gold, silver, platinum; these type of metals is what comes to mind. 

Concept #2: Group Names

Transcript

Now that we know the three types of elements that we have in the periodic table, it becomes important to be able to name the groups. And, what exactly is a group?
Now, if we take a look here, we’re going to say this is 1A, 2A, 3A, 4A, 5A, 6A, 7A, 8A. These are called your main groups. Groups go vertical. We’re going to say that there are 8 main groups. These are also called our representative elements, our main group elements.
Now, down here in the pit, these are also groups but they’re not A-groups, they’re B-groups. These are our B-group elements. They’re not representative elements. What they’re called instead is that they’re called transition metals.
You'll learn later on in the semester, why are they called transitions metals? Because a majority of these metals will have more than one charge, that’s why they’re called transition metals. They can transition from one state to another state in terms of charge. Later on, in this chapter, we’ll talk about the charges that these different groups hold, and why they hold those charges.
Again, groups 1A to 8A are called your main group metals or your representative metals. In the pit, we have our group B elements, which are your transition metals. These two columns here are also transition metals—these guys here.
Now, we’re going to say many of these representative groups also has special names associated with them. We’re going to say that group 1A, these elements are called your alkali metals, alkali metals. Hydrogen would be an exception. Hydrogen is not a metal, so it’s not an alkali metal. It’s a non-metal.
We’re going to say that the alkali metals are highly reactive. If you took for example, if you had a piece of sodium metal—pure sodium and you dumped it into water, what would happen is it will have a violent explosion with that water. And, as you go down this group to K or Rb, if you take those and throw into water, the reactions will be even more violent, leading to bigger explosions. That’s why it’s very hard to get a sample of these pure group 1A elements. You can’t just go to any store and get some. They're under lock and key, very hard to get to.
Group 2A, they’re called your alkaline earth metals. 3A and 4A and 5A, we don’t have names for them. They don’t have any general names to them. Group 6A, they’re called your chalcogens. 7A, they’re called your halogens. 8A, they’re called your noble gases or inert gases. Inert just means they don’t react with anything, very unreactive. Alkaline metals are super reactive, inert gases are very unreactive. They’re on opposite ends of the periodic table for a reason.
Now, we’re going to say that these two columns here also have names. We’re going to say that this row here, so all of this right here, these are called your lanthanides. And then this row here, these are called your actinides. They’re also transition metals but they have special names associated with them.
So, we've seen the division of the periodic table in terms of metals, metalloids, and non-metals. We’ve just seen that groups go vertical, up and down, that’s a group. Groups 1A to 8A are your representative elements or main group elements. The majority of them have a special a name associated with them. In the pit, we call those our transition metals or our group B elements.

The 3 major classifications of elements in the periodic table can be broken down as metals, nonmetals and metalloids

Different columns known as groups separate the elements in the periodic table. Each of these groups has a unique name used in their classification. 

Concept #3: Phases of the Elements in the Periodic Table 

Transcript

Now finally, we’re going to talk about the different phases that exist in the periodic table. When I say phases, I mean solid, liquid or gas. We’re going to say at room temperature and now room temperature is really a range, okay? Most people agree that room temperature is around 21 to 22 to 23 degrees Celsius. To be safe, a majority of the world will say that room temperature is anywhere between 20°C to 25°C. We’re going to say at room temperature, almost all the elements you find on the periodic table will be solids.
And, just so you can see everything I’m writing, I’m going to take myself out of the picture guys. Just remember, at room temperature all elements are solids except for a few. Here we’re going to say that mercury, now, mercury is - let me erase all of this right here - mercury is Hg which is right here, and bromine, which is right here, Br. These two elements don’t exist as solids at room temperature; instead, they exist as liquid. Just think of the mercury in a thermometer. Mercury is a liquid.
And, now we’re going to say hydrogen which is right here. Hydrogen, nitrogen, oxygen, fluorine, chlorine and the noble gases—these guys here. These guys don’t exist as solids either. They exist as gases at room temperature.
Just to give you a quick overview of what the periodic table is, who came up with the term, who do we owe this to, the classifications and subdivisions of each group, if you can understand this, it will make you a lot easier when it comes to memorizing and understand why reactions happen the way they do.

At room temperature (between 20 oC to  25oC), all elements exist as solids, liquids or gases.

Charge Distributions of the Periodic Table

Elements gain positive and negative charge when they lose or accept electrons. 

Concept #4: The Reason for Negative and Positive Ions

Transcript

We already know or should know that if an element has the same number of protons and electrons, then it's going to be a neutral element. But once we have a different number of protons and a different number of electrons, that element can either get a positive charge or a negative charge.
Now we're going to say, why do element do this? Why are elements reactive in the first place? Well, we're going to say a majority of the elements on the periodic table are reactive because they're all trying to become just like the noble gases.
Basically, the noble gases are like the rockstars of the periodic table. They're perfect because they have the correct number of electrons that fit perfectly into their outer shells. So everyone is either trying to gain or lose electrons to become just like that.
When you're gaining or losing electrons, you're going to pick up a negative or positive charge. That's the whole purpose of chemical reactions, to become more stable, to become more like the noble gases. 

Elements gain and lose electrons so that they have the same number of electrons as the noble gases, which are electronically perfect.  

Concept #5: Cations as Type I Metals vs Type II Metals 

Transcript

We're going to say that metals, metals tend to lose electrons to become positively charged ions called cations. We're going to say metals that have only one charge associated with them are referred to as Type I metals. So let's take a look.
Remember we talked about this way back, the subdivisions of the periodic table. Remember we said that there's a staircase right here, and we said that these guys here are the metalloids. So those are your metalloids. And then everyone to the right of them are going to be your nonmetals, including hydrogen and then everything else on the periodic table is a metal.
Now, we're going to say we have main group metals. We're going to say that the charge of Group 1A is +1, Group 2A is +2, Group 3A is +3. Now we're going to ask ourselves, why do these guys have these charges? Let's think about this for a second. Here we look at lithium. Lithium is Li. Lithium has three electrons. Why do we know it has three electrons? Because just say that all the elements on the periodic table are in their neutral forms.
Here, this is the atomic number. So according to the atomic number, we have three protons. Since we're assuming everyone is neutral on the periodic table, the number of protons and a number of electrons must be the same. So if my atomic number is three and I'm neutral, that must mean I have three protons, but more importantly, I have three electrons, so lithium has three electrons.
Lithium wants to become just like a noble gas. It wants to become just like a Group 8A element. Now lithium has two choices to go. It can either try to gain seven electrons to become like neon which is very unlikely or it could just lose one electron and become like helium which has two also. Remember, you always go the shortest distance to get to a noble gas. So it's better for lithium and the other Group 1A metals to lose one electron.
Neutral lithium has three protons, which are all positive, and three electrons. When it loses one of its electrons, it's now going to have two electrons and become perfect just like helium, but its number of protons have to stay the same, because if you change a number of protons, you change the identity of the element, so your number of protons are staying the same. The only thing that's changing are the number of electrons. That's how we know lithium gains a +1 charge because we have more positives than we do negatives.
In the same way, beryllium wants to lose two electrons, to become just like helium. And boron over here, boron tends to lose electrons as well. We're going to say it loses +3, so these guys here lose +3 to be become just like the noble gas. So we're going to say aluminum, for example, has an atomic number of 13, wants to lose three electrons to become ten just like neon. Again, we're going to say metals tend to lose electrons to become cations. We're going to say that Groups 1A, 2A and 3A have the charges of +1, +2 and +3.
Now, they're all Type I metals because they only have one charge. Now, we're going to say metals that have more than one charge are referred to as Type II metals. These are traditionally are transition metals. Transition metals tend to have more than one charge. Remember, we said the transition metals are the guys here in the pit. These guys tend to have more than one charge. For example, iron has two charges: +2 or +3. Chromium does too. A lot of them have more than one charge.
There are three of them, though, that even though they're transition metals, they have only one charge. The three that follow that trend are silver, which is Ag, silver is always +1, cadmium, which is Cd right next to it, is +2 and zinc, right above it, is +2. These three guys are transition metals.
We expect them to have more than charge, but they are an exception to that. These are transition metals but they're Type I transition metals. They have only one type of charge. Most of the other transition metals have more than one charge, so we would refer to the other transition metals as Type II.
Now, we're going to say also that tin here and lead, these two right here, they're both in Group 4A. Technically, they're not transition metals, but they act like it. They have more than one charge associated with them. We're going to say tin can be either +2 or +4 and lead can be either +2 or +4. Again, as an Sn and Pb in Group 4A, they're not transition metals, but they act like it. They have more than one charge. 

Type I metals are metals that possess one charge, whereas type II metals possess more than one charge. 

Concept #6: Nonmetals and anion formation 

Transcript

Here we're going to say non-metals tend to gain electrons to become negatively charged. Because, remember, if you're gaining negative electrons, you're going to become more negative. So you become negatively charged ions called anions.
If we take a look here we're going to say fluorine has an atomic number of 9. Since we assume it's neutral on the periodic table, it also has 9 electrons. Say to yourself, how many electrons does fluorine need to gain to become just like neon. All it needs to do is gain one electron. In fact, all the halogens, all the elements in group 7A, need just one more electron to become just like a noble gas. So they have a negative one charge.
Oxygen needs two more elections to become just like a noble gas. So group 6A, the chalcogens, have a negative two charge. 5A would be negative three.
Group 4A, it's kind of halfway. It can either gain or lose electrons, equal distance, so we tend not to say that they're strictly one type of charge. Carbon is a non-metals, so it won't lose electrons, but it won't necessarily gain them either. We'll learn later that carbon forms special kinds of bonds called covalent bonds. The same thing can be true with silicon right below it.
The real metals in this group are tin and lead. These two guys behave like type 2 metals. They have more than one charge. It's a lot of things to be taking in. But, just remember, things are reactive because they're trying to become like noble gases. Metals will lose electrons to become like their closest noble gas, whereas non-metals will gain electrons to become like the closest noble gas. That's the whole purpose of this.
Remember type 1 metals have only one charge. Zinc, cadmium and silver, even though they're transition metals, they have only one charge and therefore, they're type 1 metals.
Type 2 metals have more than one positive charge. These guys are typically your transition metals. The exceptions to that are tin, which is Sn, it can be plus two or plus four, or lead, Pb, which is plus two or plus four.
These are the exceptions that professors will quickly go over in class, realizing that some people may not hear it or may not write it down, but they always like to test on it. They always like to test questions on zinc, cadmium and silver, what their charges are. They always like to give questions on exams on tin and lead, what their charges are. Are they type 1 or type 2? As long as you can remember why do things have certain charges based on their proximity to the noble gases and as long as you can remember the exceptions, you'll be better prepared for this section. 

Unlike metals, nonmetals will under normal conditions gain electrons to become more like their closest noble gas.

Element Symbols

Many of the symbols used for elements are easy to recognize. However, some elements in the periodic table have Latin, Greek and other origins and so their symbol may not match their name as clearly. 

Example #1: Identify the elements by their given symbols.

Au          Hg            Pb               Fe                 Ag

Transcript

Au just represents gold. The next one, Hg, Hg we tend to find in older types of thermometers and barometers. We’re going to say that here, Hg is just mercury. Now, if you go to a dentist’s or a doctor’s office, and you have to have an x-ray done, it’s probably good to have one of these types of aprons on. It’s good to have a lead apron on. So Pb is lead. We’re going to say that usually the bars of cells in prisons or in old-fashioned handcuffs are made up of iron. And then finally, just like we have high value in gold, Ag is another precious metal that we deal with. Ag is just silver.
In terms of the elements that I’ve said that you should have looked at and try to memorize, remember it’s pretty good in your best interest to memorize the first 36 symbols. But I also suggest memorizing the ones that we just did. Most of them are not part of the first 36 elements but you still are responsible for them. So I would say memorize them. And not only those guys that are listed below, but I’d say memorize tin as well. So memorize the first 36 elements, then memorize these ones that we just did, and then memorize Sn which is tin.

Monoatomic, Diatomic & Polyatomic Elements

Concept #7: Discussing the Monoatomic Elements

Transcript

We’re going to say that when it comes to the periodic table, we’re going to say the periodic table just shows us the elements. We’re going to say that some of these elements exist in nature by themselves, some of them exist in nature connected to copies of themselves. If we look here, we say some elements exist in nature connected to their exact double. We’re going to say that these chemical Siamese twins are called diatomic molecules.
Now to help you remember, there are seven of them and to help you remember which one of them are diatomic, just remember this funny phrase, ‘Have No Fear Of Ice Cold Beer’. It might seem funny, but trust me it works. It helps memorize these really quickly. So H2, N2, F2, O2, I2, Cl2, Br2, so this is what we’re supposed to take away from this funny phrase. So these are your seven diatomic molecules.
In some books, some books talk about an 8th diatomic molecule. But it’s kind of random if your professor chooses to talk about it or not. So here we’re going to say that At is one of the halogens, it’s in the group with the halogens. It can also exist as a diatomic molecule, so it could exist as At2. The thing is it’s kind of random if professors choose to talk about it or not. But just have it stowed away at the back of your mind, that At could also be a diatomic molecule.

Many elements in the periodic table exist naturally by themselves, such as sodium metal, Na (s). 

Concept #8: Discussing the Diatomic and Polyatomic Elements

Transcript

Besides being diatomic, when I say some exist in nature as monoatomic elements. Monoatomic just means they are found by themselves. Basically, a majority, or all of the metals exist as monoatomic elements. So sodium, lead, aluminium, in nature they exist by themselves, just one of them. Not as diatomic molecules, just as monoatomic elements.
We also say that carbon can also exist as monoatomic element. Carbon can exist as C (graphite). So this is one of the natural forms of carbon. Now if you look at your pencil, most people may think their pencils are made out of lead. The thing is, the lead was removed from most pencils years ago because of lead poisoning. Now, the lead found in pencils are not lead, they’re graphite. So you’re writing using graphite with your pencils. And this is a natural form of carbon. Carbon can also exist as diamond. That’s another natural form of carbon.
Now, I’m going to take myself out of this image so I don’t block anything else. Finally, we’re going to say that some elements exist in nature as polyatomic molecules. When I say polyatomic, that means that more than two of itself will bond together. So diatomic means two of them together, polyatomic means more than two of them together. And the two best examples of polyatomic molecules are phosphorous, because phosphorous can exist as P4, or sulfur, sulfur can exist as S8. In both of these examples, we have more than two of them combining with each other to from the molecule.
So just remember, you have to memorize the first 36 elements, the symbols. Just the symbols and the names associated with it. Memorize the Latin root names that we did in the first example as well as tin.
From that, you should also remember your diatomic molecules. Professors love giving questions on diatomic molecules because they realize that most students either don’t know it or they easily forget who they are. So just remember, who are the diatomic molecules because. trust me, when we get to sections on gases, get to sections on mass conversions, it’s going to be essential that you know who are your diatomic molecules and what does the compound look like before I begin any types of calculations. So keep memorizing those groups, it’ll help you tremendously later on in the chapter, later on in the semester. 

Some elements in the periodic table exist in pairs called diatomic elements, just remember them with:

Ice exists as a solid so the natural form of I2 is a solid. Beer exists a liquid so the natural form of Br2 is a liquid. The remaining diatomic elements exists as gases. 

Polyatomic elements exist as more than a pair of elements together, such as phorphorus which exists as P4