Chemical Formulas

Chemical Formulas

How are chemical formulas used to identify substances?

ELEMENTS

• A chemical that cannot be broken down into another substance.

• Each unique capital letter represents a different element.

ELEMENTS

• How many elements are in glucose?

ATOMS

• The smallest part of a chemical element.

MOLECULES

• Combining atoms creates molecules.

Formula for Molecules

An expression which states the number and type of atoms present in a molecule of a substance.

*H₂ tells you there are 2 atoms  of hydrogen.

H₂O tells you

2 atoms of hydrogen

and

1 atom of oxygen.

SUBSCRIPTS

• The small numbers after the element’s name.

• No subscript means there is  only 1 atom present. (The one is not needed.)

Counting Atoms

1. List the elements.

Cu

S

O

2. Record the atoms of each element.

Cu-1

S-1

O-4

Multiple Choice

Which of the following chemical formulas contains exactly 4 hydrogen atoms?

• CH₃COONa

• NH₄OH

• CH₃CH₂Cl

• CH₃CHO

Multiple Choice

How many atoms of carbon are in the formula CH₃CH₂CH₂OH?

• 3

• 1

• 7

• 4

Multiple Choice

How many atoms of hydrogen are in the formula CH₃CH₂Br?

• 5

• 3

• 2

• 7

Multiple Choice

Which elements are in the formula shown above?

• Tin and Chlorine

• Tin, Carbon and Lithium

• Sulfur, Nitrogen and Chlorine

• Sulfur, Nitrogen, Carbon and Lithium

Multiple Choice

Which of the following accurately describes the chemical formula of the molecule shown above?

• 3CH₈O

• C₃H₇O

• C₄H₈O₂

• C₃H₈O

Multiple Choice

How many Oxygen atoms (O) are in a  molecule  of CO₂

• 1
• 2
• 3
• 0

Multiple Choice

Sodium sulfate is used in laundry detergent. It is a compound that contains 2 atoms of sodium, 1 atom of sulfur, and 4 atoms of oxygen. What is the correct chemical formula for sodium sulfate?

• NA₂SO₄

• Na₂S₂O₄

• Na₂SO₄

• Na₂SO₈

Multiple Choice

In this compound structure of alcohol, how many Hydrogen atoms are there?

• 2
• 4
• 6
• 8

Multiple Choice

How many atoms of Hydrogen are in this compound

• 1
• 2
• 3
• 4

Multiple Choice

How many atoms of Hydrogen are in this compound

• 1
• 2
• 3
• 4

Multiple Choice

What elements are represented in this chemical formula?  $Fe_2O_3$  

• Iron, Oxygen

• Francium, Europium, Oxygen

• Ferrium, Oxygen

• Berylium, Oxygen

Multiple Choice

How many atoms of Carbon are in this formula? $C_{6\ }H_{12}O_6$  

• 6

• 1

• 12

Multiple Choice

What does the subscript in a chemical formula tell you?

• How many molecules are present

• How many atoms are present

• How many elements are present

• How many neutrons are present

Subscripts + Coefficients

Big number at the  beginning of this formula is a coefficient.

Represents the number of molecules for that compound

Subscripts + Coefficients

This formula means there are 2 H₂SO₄ molecules.

We know in each molecule there are:

   2 hydrogens

   1 sulfur

   4 oxygens

To find the total number of atoms:

multiply each of these atoms by 2.

 2 hydrogens x2

 1 sulfur x2

 4 oxygens x2

Total atoms for this formula = 14