Chemical Formulas

Chemical Formula:

An easy way for scientist to describe a molecule using the element symbols.

H2

OC02

NaCl

REMEMBER…When you read a chemical

formula, each new element begins with a capital letter. So if you see CO2, you should think Carbon and Oxygen.

However…If you see a lower case letter in a

chemical formula, it goes with the capital letter that comes before it. For example:

If you see NaCl, you should think (Na)Sodium and (Cl)Chlorine.

Reading Chemical Formulas

NaCl Sodium Chlorine

Reading Chemical Formulas

H2O

Hydrogen Oxygen

Subscript – number that follows a symbol; subscript tells how many atoms of element are in molecule

This subscript tells us thereare 2 atoms of hydrogen inthis formula.

If no subscript is present, it is understood thesubscript is 1. So there is 1 Atom of oxygen in this formula

Reading Chemical Formulas

2H2O

Coefficient: The large number before an element symbol or compound that

represents the number of elements or compounds. You multiply the coefficient by

the subscript to find the number of atoms of each element.

Hydrogen Oxygen

The coefficient shows us there are 2 molecules of water in this formula.

The coefficient in this formula tells us there are 4 hydrogen atoms and 2 oxygen atoms

Reading Chemical Formulas

2CO2 Carbon Oxygen

What elements are bonded to create this molecule of Carbon Dioxide?

How many atoms of each element are in this molecule of Carbon Dioxide?