Ionic vs. Molecular


In this video we’re going to look at compounds
that are ionic versus compounds that are molecular also known as covalent. We will learn how
you can tell them apart based on their formulas and then we’ll look at some important differences
between them. So how can you tell whether something is ionic or molecular? Well it depends
on the elements that may come up. So ionic compounds are made of metals and nonmetals
whereas molecular also known as covalent compounds are made of only nonmetals. Let’s do a couple
practice problems to work on this. You will need a periodic table to do this, here’s the
one that I’m using, I’ve left out a lot of the elements because they’re not important.
But what is important is this big thick staircase that divides the periodic table into two parts.
On this side of the staircase are the medals and on this side of the staircase are the
nonmetals. Okay, so here are a couple examples. The first one, Sulfur Dioxide, so where are
the elements that it�s made of. It’s made up of Sulfur and oxygen, both these are nonmetals,
which means that Sulfur Dioxide (SO2) is a molecular compound. Sodium Chloride is made
up of Sodium, a metal, and Chlorine or Chloride which is a non-metal. Sodium Chloride is an
ionic compound. Alright now, H2O is made of Hydrogen and Oxygen. Now you might think that
Hydrogen is a metal because it’s on this side of the periodic table, it�s fine and understandable
if you do that. But Hydrogen is an exception, even though it’s on this side of the periodic
table it�s actually a non-metal, it’s the only exception. So Hydrogen and Oxygen are
actually both nonmetals which means that H2O water is a molecular or covalent compound.
Okay Copper (II) Fluoride, Copper is here and Fluorine or Fluoride is here, metal, non-metal
so this thing is ionic. Okay, let’s look at a few trickier examples. So far, we’ve only
look at compounds that have two elements but there are a lot of compounds out there that
have more than two elements, okay? So Propanol for example is made up of Carbon, Hydrogen
and Oxygen. All three of these are non-metals though so this is still a molecular or covalent
compound even though it has a bunch of nonmetals, okay? Don’t be confused by that. Here’s another
example. Lithium Nitrate has Lithium which is a metal but then it also has Nitrogen and
Oxygen which are both nonmetals. So it still has that metal, nonmetal thing going on so
it’s an ionic compound even though it has two nonmetals and the same thing is true of
Sodium Sulfate. It’s got Sodium, a metal, and two nonmetals, Sulfur and Oxygen but metal
and nonmetal means it�s ionic. Now Lithium Nitrate and Sodium Sulfate are actually special
kinds of ionic compounds because they have two different nonmetals in them. They are
what are called polyatomic ionic compounds and if you want to learn more about these
I’ve got videos on them. So now we can look at a chemical formula and we can sort them
and we can decide whether something is ionic or whether it�s molecular or covalent. So
what? Who cares? Well there are some very important differences between ionic compounds
and molecular compounds. Let’s take a look at some of those right now. So one really
important difference is how the atoms in these compounds are held together. In molecular
or covalent compounds, the atoms that make them up are held together because they’re
sharing electrons. Here’s what I mean. Water, H2O, is a very common molecular compound.
It’s made up of one Oxygen and two Hydrogens and these lines between the atoms show they’re
connected and they mean that they’re connected because they’re sharing electrons. Here’s
how I like to think about this. It’s like Oxygen and Hydrogen both have these little
hands and the hands are joined together, it�s like their holding hands and they’re holding
hands because they both are trying to hold on to a pair of electrons which I’ve drawn
here in red. You got Oxygen and Hydrogen connected together because they’re holding on and sharing
these electrons here, that’s what makes atoms connect and stick together in a molecular
or covalent compound, okay? Now on the other hand, in ionic compounds, atoms aren�t being
so nice to each other�they’re not sharing. The atoms stick together in an ionic compound
because one atom steals another atoms electron, so electrons get stolen, and then opposite
charges attract. Let me show you what I mean. So Sodium Chloride or NaCl is a very common
ionic compound, it’s made up of Sodium and Chlorine and here they are just hanging out.
Now for these two guys to stick together, here is what happens. The first thing that
happens is Chlorine reaches its greedy hand over and grabs an electron from Sodium, okay,
and it pulls it back. So now, Chlorine has an extra electron and Sodium has lost one
of its electrons. This causes Chlorine to now get a negative charge because it has a
new electron and Sodium because it had one of its electron stolen now it has a positive
charge. So now we have a positively charged ion here and another negatively charged ion
here. What do opposite charged things like to do? They like to come together, they stick
together, they are attracted to each other just like magnets. So now, we have a positively
charged thing and a negatively charged thing. These arrows show how they’re going to come
together and we end up with the two atoms stuck together because they’re oppositely
changed and that’s what holds ionic compounds together. So covalent or molecular compounds,
the atoms are stuck together because they’re sharing electrons with each other. Ionic compounds,
atoms are stuck together because one has stolen the others electrons, it’s given them opposite
charges and then those opposite charges have attracted just like magnets. That is one way
that ionic and molecular compounds differ. Here is one more. So another big difference
is how these compounds would actually look if we could see the atoms that make them up.
So molecular or covalent compounds are made of molecules, which is a fancy word for a
bunch of atoms that are stuck together in a clump. Here’s what I mean. So sugar is a
very common type of a covalent compound and it is made of molecules, where I have these
atoms here stuck together in a clump– two Carbons, four Hydrogens and two Oxygens. So
a grain of sugar would look like this, it would look like a number of different sugar
molecules that have all kind of come together and formed a clump here, okay? But the big
deal here is that these molecules are individual clumps of atoms that then come together to
make stuff. On the other hand, ionic compounds� they’re not made of clumps of atoms like molecules.
They�re made of what we call lattice structures and here’s what lattice structures are. The
example I’m going to give you is salt which is Sodium Chloride table salt and the lattice
structures of Sodium Chloride look like this. Look how different this is from the molecules
that makeup sugar. You just have the Sodium and the Chloride atoms stuck together in this
very organized box-like shape. This is what a lattice structure is. There aren�t individual
clumps of Sodium Chloride the way there are individual clumps of sugar, instead all the
atoms are stuck together in this very regular shape. Now one big important difference between
covalent or molecular stuff and Ionics is what happens when they dissolve in water.
These guys just come apart into molecules whereas the individual atoms come apart when
an ionic compound dissolves in water but we’re getting a little ahead of ourselves here.
If you’re interested other differences between these, check out videos that I have on physical
properties as well as what happens when you dissolve ionic and molecular compounds.

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