All about Elements and Compounds


An element is a pure substance that can't be seperated into a simpler substance.

-Example: Aluminum


A compound is two or more elements chemically combined.

-Example: Salt


Compounds are formed from similar substances by chemical reactions. Compounds are seperated by chemical reactions. Any substance that contains only one kind of an atom is known as an element, because atoms can't be created or destroyed in a chemical reaction, elements can't be broken down into simpler substances by these reactions.

Similarities & Differences between Elements and Compounds

Elements are a substance in its simplest form, they can't be broken down by either chemical or physical means. (ex. Sodium, Na)

Compounds are substances composed of two or more elements chemically combined together. They can't be broken down by physical means, but can be broken down through chemical reactions. They both are pure substances. Compounds have two or more differnt types of atoms, while elements are pure substances that have the exact same type of atom.

Chemical Formulas

A chemical formula of a substance is a notation that uses atomic symbols with numerical subscripts to convey the relative proportions of atoms of each element in that substance. In a chemical formula, the chemical symbol of each element is shown with subscript numbers which tell us the numbers or ratio of atoms in the compound or molecule element.

-Example: H2O=water

Element Properties

When an elements properties form into a compound, they lose their properties. The properties that form it are not the same as the properties of the compound. If the compound seperates back to the elements that formed it, they would regain their properties when it seperates and a compound can only be seperated by a chemical reaction.

Coefficient and Subsripts

Coefficients are numbers used to multiply a variable. A number or symbol multiplied with a variable or an unknown quanitity.

-Example: 2H2 + O2 ---- 2H2O (The two's at the very front. before the H's both times.)

Subscripts are a distinguishing symbol as a letter or numeral written immediately below or below and to the right or left of another character.

-Example: CO-----CO2

How to count Elemements and Atoms in a Chemical Formula

To count atoms, use the subscript to find how many of each type of atom there is. If a coefficient is present, multiply the subscript and coeffiecient to find the total amount of atoms for that given element.

-Example: 9H2O=19 atoms

The chemical formula identifies each element by its chemical symbol and indicates the number of atoms of each element found in each molecule of that compound. If a molecule has more than one atom of a particular element, thee quantity is indicated using a subscript after the chemical symbol and also can be combined by more chemical elements.

-Example: Carbon, Hydrogen, and Oxygen = C6H12O6