Elements, Compounds, and Formulas

What they are, what they do, and how to read them!

By: Payton Chronister Pd. 1


Element- a pure substance that cannot be separated into simpler substances. An example of an element is Boron, and it is shown in the picture to the right.


Compound- 2 or more elements chemically combined.  The picture on the left shows water, which is the elements Hydrogen and Oxygen combined.

Elements Creating Compounds

When elements join together to create compounds, they lose their individual properties (both chemical and physical).  This is because when the elements combine, they create new properties for the new compound, and this causes them to lose their old properties.  As you can tell, the properties of the compund are NOT the same as the properties of the elements that formed it.  However, if a compound separates back into the original elements, those elements will regain their individual properties.

How Are Compounds Formed?

A compound is formed by the means of a chemical reaction.  Compounds can be formed directly from elements when 2 or more elements bound together, or they can be formed when there is a reaction between an element and a different compound. Lastly, compounds can be formed when there is a chemical reaction between 2 pre-existing compounds.

How Are Compounds Separated?

Compounds can be separated, but they cannot be separated by physical means.  The only way to separate a compound is by using chemical means such as electrolysis or combustion.  While compunds CAN be separated, an element CANNOT because it a pure substance at its simplest form.


While elements and compounds are very different, they do have some similarities such as their properties.  Both an element and a compound have chemical and physical properties.  Another thing they have in common is that they are both composed of atoms.  Lastly, both of these things have a fixed melting and boiling point.


Now that you know the similarities, let's look at some differences.  One difference is that elements cannot be separated, but compounds can.  Elements are also a simple substance, while compounds are a combination of different elements.  Another difference is that in an element, there is no bonding of different atoms, but in a compond, there is a certain form of bonding going on between different atoms.  Lastly, an element can be either metallic or non-metallic, but a compound can be a combination of both metals and non-metals.

Chemical Formulas

Chemical Formula- A representation of a substance using symbols for its elements. Another definition for chemical formula is a notation utilizing chemical symbols and numbers to indicate the chemical composition of a pure substance. When you use a chemical formula, you are expressing the composition or structure of a chemical compound.  Chemical formulas for molecules use chemical symbols with subscript numbers to show the number of atoms for each element. There are a few examples of chemical formulas shown to the right.


Coeffiecient- a number or symbol multiplied with a variable or an unknown quantity.  The picture on the left shows an example of a coefficient.


Subscript-written below; in chemistry, it is a small number written below an elemental symbol to show the number of atoms for that element.  The picture to the right shows an example of a subscript.

How To Read Them

To find the number of elements in a chemical formula, you simply count the number of element symbols. Element symbols alway start with a capital letter and end with a lowercase letter. To count each element, just count all of the capital letters.  You need to ensure that you do NOT count the lowercase letters because you will be recounting the previous element. If you want to count the number of atoms in a chemical formula, you would look at the subscripts. The subscript will always go with the element symbol written before it.  The subscript shows how many atoms of that element there are. In example, if you have a subscript of 12, then there are 12 atoms for that element. If there is not a subscript after an element symbol, it just means that element only has one atom in the formula.  Make sure you do NOT leave those atoms out in your final count! To find the total number of atoms in a chemical formula, add up all of the subscripts in that formula.  The picture on the left will show you the different parts of a chemical formula if you are still confused.