How Many Molecules Are in a Mole?

Knowing how many molecules there are in a mole can unlock a whole new understanding of the world around us. Atoms, ions, and molecules are the smallest building blocks of the universe, and counting them is a real feat. So, how do we do it when all of our equipment dwarves our object of study? Well, chemists have thought of a way to count exactly how many particles are inside any amount of a substance with extreme precision — a unit called the mole.

In this article, we will discuss the following topics:

• Are moles and molecules the same?
• What’s the relationship between the volume of a molecular substance and the number of particles it contains?
• How many molecules are there in 1 mole of molecules?
• How many atoms are there in a mole?
• How many ions are there in a mole?

If you’re curious to discover how many molecules there are in a mole, and much more, read on! You can also check out our moles to atoms converter for an easy way to perform your molecular calculations. ⚗️

At first sight, the concepts of moles and molecules might seem very close, mainly due to the similarity between the words themselves. But are moles and molecules the same?

The short answer is no.

A molecule is simply a group of atoms bonded together. For example, $\rm H_2O$ is a water molecule, while $\rm CO_2$ is a molecule of carbon dioxide. These tiny particles constitute all the molecular substances that surround us. But how do we know how many molecules there are in a gram of water, for example?

No matter how long you stare at your water bottle, you will never be able to see all the $\rm H_2O$ molecules that are inside, let alone count them. And don’t even think about using a microscope — even the most powerful tool won’t help you find the exact number, unless you have a lot of time to spare. And we mean, a lot.

So, how do chemists do it?

At the beginning of the 19th century, an Italian man named Amedeo Avogadro noticed a correlation between the volume of a gas and the number of molecules it contains. This thought was revolutionary, but it wasn’t until 1865 that Josef Loschmidt put a value to that theory, eventually leading to what we now know as Avogadro’s number or Avogadro’s constant.

$6.02214076 \times 10^{23}$

This number describes a mole, and you can often find it in its abbreviated form, $6.022 \times 10^{23}$. It represents exactly how many particles (atoms, molecules, ions) there are in a mole of any substance. Scientists often refer to this number as the chemists’ dozen — why would you ask for 24 eggs, when you can say “two dozen”? Or “36 dozen” instead of 432? In the same way, a chemist can say that there are 3 moles of water, as opposed to $18.8066 \times 10^{23}$ molecules.

Whether you have a mole of water, a mole of gold, or a mole of doughnuts, the count will always be the same. So, whenever you ask yourself, “How many molecules are in 1 mole of molecules?”, the answer is always Avogadro’s number.

How big is Avogadro’s number?

Avogadro’s constant is so large that it’s hard to wrap one’s head around it. Even though it doesn’t seem that scary in scientific notation, if you were to write it down in its entirety, it has 24 digits:

$602,214,076,000,000,000,000,000$

Let’s get our imagination going to truly grasp how many molecules there are in a mole!

• A mole of doughnuts would cover the entire planet Earth with a layer five miles deep.
• If you had a mole of pennies and spent one million dollars every second of every day, it would take you billions of years to spend that fortune. You would die of old age with 99.99% of your money still sitting in your bank account.
• A mole of basketballs would be as big as the Earth.

Can you see it now? It’s a lot!

As you can imagine from the sheer size of Avogadro’s number, chemists never count particles one by one — they weigh them instead. This is where stoichiometry comes in.

No matter what, you will always need a calculator to figure out the math behind particle counts. However, it’s also crucial to understand how the calculations work.

1. How many atoms are there in a mole?

A mole of carbon dioxide has exactly $6.022 \times 10^{23}$ $\rm CO_2$ molecules, but how many atoms does it contain?

The answer will always depend on your base molecule. Let’s calculate it:

• A molecule of carbon dioxide has three atoms: $\rm C$, $\rm O$, and another $\rm O$. These are joined by double covalent bonds.
• A mole of carbon dioxide has $6.022 \times 10^{23}$ molecules.
• Therefore, a mole of carbon dioxide has $3 \times 6.022 \times 10^{23}$ atoms.

2. How many ions are there in a mole?

Here, the focus shifts to charge.

Take magnesium chloride ($\rm MgCl_2$). When this salt dissolves in water, it falls apart. One unit of $\rm MgCl_2$ becomes one magnesium ion ($\rm Mg^{2+}$) and two chloride ions ($\rm 2Cl^-$). That’s three ions for the price of one unit.

• 1 mole of $\rm MgCl_2$ contains $6.022 \times 10^{23}$ units.

• So, how many ions are in a mole of $\rm MgCl_2$?

  The answer is:

  $3 \times (6.022 \times 10^{23}) = 1.807 \times 10^{24} \text{ ions}$

We hope you have enjoyed this journey through the microscopic world of particles, and that we have helped you understand the difference between moles and molecules. When in doubt, remember: the answer to the question “How many molecules are there in a mole?” is always Avogadro’s number! Whether you are balancing a chemical equation for a school project or just wondering how many atoms are in a drop of water, the mole is your trusty translator.