What is a Chemical Formula? - Definition, Types & Examples

What is a Chemical Formula? - Definition, Types & Examples
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  • 0:05 What is a Chemical Formula?
  • 1:28 Molecular Formula
  • 1:57 Empirical Formula
  • 3:06 Structural Formula
  • 3:59 Condensed Structural Formula
  • 4:43 Lesson Summary
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Lesson Transcript
Instructor: Nissa Garcia

Nissa has a masters degree in chemistry and has taught high school science and college level chemistry.

Chemical formulas provide a lot of information about chemical substances, such as how many and what atoms they are made of, as well as the way the atoms are arranged. In this lesson, we'll discuss the different types of chemical formulas.

What is a Chemical Formula?

We encounter chemical substances and compounds everyday. The substances under the kitchen sink that we use to clean our houses as well as those that are staples in our medicine cabinet are made up of chemical substances. These chemicals are made up of a fixed proportion of atoms, and these atoms are arranged in a certain way. In order to figure out what these proportions are and how they are arranged for any given substance, we need to know the chemical formula of the substance or compound.

Chemical Substances in Our Medicine Cabinet

A compound is a substance made up of a definite proportion of two or more elements. A chemical formula tells us the number of atoms of each element in a compound. It contains the symbols of the atoms of the elements present in the compound as well as how many there are for each element in the form of subscripts.

Compounds and Chemical Formulas

Each chemical substance has a specific chemical composition, so these chemical substances have their own chemical formula. Let's take a look at the chemical formula of glucose: there are 12 carbon (C) atoms, 22 hydrogen (H) atoms and 11 oxygen (O) atoms.

There are different types of chemical formulas and each type gives us different information about a chemical substance. The different types of chemical formulas include: molecular, empirical, structural and condensed structural formulas. We'll discuss each of these different types as well as go over a few examples.

Molecular Formula

The molecular formula, sometimes known as the true formula, tells us the actual number of the different elements in one molecule of a compound. In a molecular formula, each element is written as their symbols in the periodic table, and the number of atoms for each element is shown by the subscript (the small number to the lower right of the element). Here are some examples of molecular formulas:

Molecular Formula

If we look at butane, we see it has 4 carbon (C) atoms and 10 hydrogen (H) atoms.

Empirical Formula

The word empirical is defined as something that is verified by observation. In chemistry, we verify facts by performing experiments. So, the empirical formula is defined as the simplest ratio of whole numbers of elements that make up a compound, and this type of formula is derived from experimental data.

Just like how we simplify fractions in math class, in chemistry we can simplify formulas as well. In this case, let's look at the molecular formula of glucose:

How to Get the Empirical Formula

While the molecular formula gives us the actual number of atoms of each element in a molecule, the empirical formula gives us the simplest ratio and not the actual number of atoms of an element. Here are some examples of empirical formulas derived from molecular formulas:

Empirical Formula

Sometimes, there are molecular formulas that are already at their simplest ratio which means they cannot be further reduced. In these cases, the molecular formula is the same as the empirical formula which can be seen with these examples.

Empirical and Molecular Formulas Are The Same

In Sucrose, the subscripts 12, 22 and 11 do not have a greatest common factor, so they cannot be further reduced. The same goes with ethanol.

Structural Formula

When we simply write the molecular formula, we do not know how the atoms are arranged or which atoms are bonded to each other. The structural formula shows both the actual number of atoms of elements in a compound, how the atoms are arranged and which atoms are bonded to one another.

Here are the structural formulas of ethane, propane and ethanol. The molecular formulas of each are reflected below the structural formulas.

Structural Formula

Let's look at ethane. It shows that the carbon (C) atom on the left is bonded to three hydrogen (H) atoms and the other carbon atom. The carbon on the right is also bonded to three hydrogen atoms and the carbon on the left.

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