Understanding Atomic, Molecular Elements and Ionic vs Molecular Compounds

You might remember this figure. We learned that matter is composed of pure and mixtures. Pure substance and

mixtures. And pure substances are elements and compounds. That's what we learned so far. And now we will see that

these elements we can divide them into two parts. Atomic elements and molecular elements. Atomic elements exist as

atoms. I briefly touched on that before. Copper is a a metal. Most metals exist as atoms. You will never see oxygen

atoms in nature. You will always have two oxygen atoms combined together. That's why we write oxygen O2. Basically

what I'm trying to say is if you have oxygen balloon and a balloon of helium and if we zoom it in or if we have

technology to see what are the particles when you zoom in what you will see in oxygen is there are always two oxygen

atoms combined together and you will not see single oxygen atoms but helium you will see single helium atoms. So they

are elements they exist as atoms. They are called atomic elements because they exist as atoms. Some other one are

copper. Most of the metals copper, aluminum and gold, silver like that. But oxygen will be always like O2 and not

only oxygen there are some other gases as well. We will see later. Neon also these all these gases noble gases inert

gases they exist as single atoms because they are stable. The oxygen or florine or chlorine they occur as two atoms. We

call it diatomic. We will see later the reason oxygen occurs as O2 or hydrogen occurs as H2 because this is the stable

form. Oxygen atom is not stable. Hydrogen atom is not stable. They always have to combine with somebody. But these

noble gases are not. These are molecular elements because they exist as molecules. And also just for our

knowledge, I'll just go go a little ahead of myself. This is something you have to remember. Iodine, bromine,

chlorine, florine, oxygen, nitrogen and hydrogen. These are all exist as diatomic. Di means two carbon dioxide.

Diatomic molecules mean hydrogen exist as H2 and nitrogen exist as N2. You will not see nitrogen atoms in nature.

Florine as F2 like that. Therefore, they are molecular compounds. This is what you have to remember. But there are two

other things you don't have to remember, but it's good to know. Phosphorus and sulfur, they do not exist as atoms, but

they do not exist as diatomic molecules as well. Phosphorus usually exists as P4. There are four atoms and there are

multiple molecules of sulfur. Most stable one has eight sulfur atoms. Again, elements may be atoms or

molecules. This is mercury. Mercury exist as atoms. This is chlorine. Chlorine is always diatomic. These are

the diatomic molecules. Please remember. Yeah, you can see except bromine and iodine. Iodine is a solid at room

temperature. Bromine is a liquid at room temperature. Others are gases. We just discussed about elements they can be

atomic or molecular. Now let's go to the compounds. Compounds can be molecular or ionic. We know in compounds there are

two or more different types of elements. And let's see what the difference between molecular and ionic compounds.

These molecular compounds sometimes we also call covealent compound. They are formed when there are two or more

non-metals bonding together. For example, our favorite example water. Water we know this is hydrogen. Even

though hydrogen is here in the metal section, we know that hydrogen is a nonmetal. And also we know why it is

here because it has one veence elect. Hydrogen is a nonmetal. Oxygen is a non-metal. Therefore, water is a

molecular compound. Similarly, sulfur diox is a nonmetal and oxygen is a nonmetal. Therefore, it is a molecular

compound. Ammonia NH3 N is a non-metal. Hydrogen is a nonmetal. Nitrogen and hydrogen. Therefore, they are molecular

compounds. Same with sucrossse or sugar. Let's talk about bonding in these molecular compounds. In molecular

compounds, we have nonmetals and nonmetals. So, how are these atoms holding together? This is a water

molecule. And I this is actually a better representation of water. We have bonding between hydrogen and oxygen.

There are two bonds. The bonding in molecular compounds are called covealent bond. Coalent bonds. That's the reason

we call these compound as covealent compound as well. So what are coalent bonds? Coalent bonds

are formed when electrons are shared between atoms. Here we have hydrogen atom and oxygen atom. So actually this

bond is a pair of electrons shared between these two atoms. So this is a beta one here. So we have hydrogen atom

and oxygen atom. So these two electrons are shared between these two atoms. This shared electrons is actually the

chemical bond. Since it is shared we call it a covealent bond. Next we will learn about ionic bond. Then you will

see in ionic bonds electrons are not shared. It's completely transferred from one atom to another one. There are no

sharing in ionic compounds and ionic bonds. So these are the two coalent bonds. How can these shared electrons

keep these atoms together? For that we have to consider the charges. We know these atoms have nucleus. So this is the

nucleus of oxygen atom. This is the nucleus of hydrogen atom. We know they are positively charged. And also we know

electrons are negatively charged. For that reason, these shared electrons can attract both atoms, both nucleus.

Therefore, it can keep both atoms together by this attraction between electrons and two nucleus. So, ammonia

like this, these are shared electrons and coalent bonds. One important thing to remember is these coalent bonds exist

within the molecule between atoms. When we have two water molecules, let's say oxygen, hydrogen and hydrogen. Please

understand there are no coalent bonds between molecules. You cannot find coalent bonds between molecules. For

that reason, these molecules can we can separate these molecules. They are free to move. They exist as individual

molecules. That is a unique characteristic of molecular compounds because you will see later add compounds

do not exist as individual units but molecular compounds exist as individual units because there are no coalent

bonding between individual molecules. The other compound is ionic compound. Ionic compound form from metals and

nonmetals. Again my favorite example is sodium chloride. Sodium is a metal and chlorine is a non-metal. When sodium and

chlorine together when you form sodium chloride it is an ionic compound. It says it contains cation paired with

annions. Don't worry about that. I will discuss in detail later. Sodium is a metal and sodium or metals try to lose

electrons and form cations. We know why sodium is losing one electron because it needs to get the same electrons as neon.

And also we discussed that chlorine is a nonmetal. When chlorine forms ions, chlorine will take electron in this case

one electron and become like argon. So chlorine will take electron and it will become chloride ion cl minus. What I

didn't tell you at the time is that this sodium want to lose electrons and become sodium ion because it is stable. It is

stable because it is like neon. But just because sodium wants to be like neon and become sodium ion, it cannot do it

unless there is somebody to accept that electron. You just cannot throw an electron to the thin air and become a

cation. There has to be somebody to receive it. In this case, chlorine receives that electron and it becomes an

ion because chlorine is always wanted to get an electron and become like argon. Now what we have is cation and annion.

Since ionic compounds have ions, they can conduct electricity when ionic compounds are in the liquid state or in

solutions, not in the solid state. Because in liquid state and solutions, you have moving ions. To conduct

electricity, we need to have moving charged particles. Here we have moving ions. That's the reason ionic compounds

conduct electricity when they are in the liquid state or dissolved in solutions. We know they're positive and negatively

charged. And also we know that positive and negative charge attract each other. I'll try this chloride here. Basically

when this happens when you have these two types of ions since they are oppositely charged there will be an

attraction. This attraction is called ionic bond. So ionic bond is attraction between anion and cation. For now just

understand these ionic compounds are formed from metals and nonmetals and during their formation you will have

ions in this case sodium and chloride ions and they have ionic bonds. Therefore they are called ionic

compounds important in this case is metal and nonmetal. Now we are going to learn a very important concept very

simple but extremely important because I have seen students make these mistakes over and over just because they don't

understand it. Now we know that ionic compounds are composed of annions and cations and when we write sodium

chloride in this case we write ncl since it is a ionic compound in other way metal and nonmetal sometimes I

repeat myself a lot please bear that the reason I'm doing it because I'm trying to emphasize for those who may not

understanding the first time we have a metal and a non-metal ionic compound when we write sodium chloride as this It

is very different from when I'm writing water or carbon dioxide. We know that water and carbon dioxide are molecular

compounds because they are formed from non-metal and nonmetal. Non-metal and nonmetal. But there's a much bigger

difference how they appear in nature. For example, if I have a basket of water and if I can break it into small parts,

I will have small water droplets and finally I will be able to get individual water molecules. Individual water

molecules I can do that that's how they exist. Similarly, carbon dioxide I can have small carbon dioxide particles CO2

exist together. So because they exist as molecules. We know molecules have more than one atom. But in these ionic

compounds they do not occur as molecules. Even though I write this N as NAC we never say this is NAC molecule

because ionic compounds don't exist as single particles exit as giant latice or 3D array. So basically what it has here

is in green you see chloride ions. There are multiple sodium atoms attached to that chloride ion. Similarly if you get

a sodium atom sodium atom is attached to multiple chloride ions. This is a giant threedimensionally connected latice.

Sodium chloride does not exist as individual units. The only reason we show it here as just one NaCCl it looks

like a molecule because that's the easiest way we can say. We cannot write this one when we are writing our

day-to-day life. If this sodium chloride is not a molecule, what is it called? It is called a formula unit. Formula unit.

This formula unit is the smallest electrically neutral unit of an ionic compound. This is the smallest unit and

electrically neutral. What does that mean? We know sodium is positive one, chloride is negative -1. When they are

together in the ionic compound, it is electrically neutral. Electrically cancel out. This is called formula unit.

It is not a molecule. Please understand those two differences between ionic compounds and molecular compound. In

ionic compounds, you will not see molecules. Don't say sodium chloride molecule. You can say just sodium

chloride compound or sodium chloride formula unit. You can see here they're showing a formula unit. That's the

easiest way to