CK-12 Physical Science - For Middle School

7.1. Introduction to Chemical Bonds http://www.ck12.org

TABLE7.1:(continued)

Name of Compound Electron Dot Diagram Numbers of Atoms Chemical Formula

Hydrogen chloride H = 1

Cl = 1

HCl

Methane C = 1

H = 4

CH 4

Hydrogen peroxide H = 2

O = 2

H 2 O 2

Carbon dioxide C = 1

O = 2

CO 2

Problem Solving

Problem:A molecule of ammonia consists of one atom of nitrogen (N) and three atoms of hydrogen (H). What is
its chemical formula?

Solution:The chemical formula is NH 3.

You Try It!

Problem:A molecule of nitrogen dioxide consists of one atom of nitrogen (N) and two atoms of oxygen (O). What
is its chemical formula?

Same Elements, Different Compounds

The same elements may combine in different ratios. If they do, they form different compounds.Figure7.2 shows
some examples. Both water (H 2 O) and hydrogen peroxide (H 2 O 2 ) consist of hydrogen and oxygen. However, they
have different ratios of the two elements. As a result, water and hydrogen peroxide are different compounds with
different properties. If you’ve ever used hydrogen peroxide to disinfect a cut, then you know that it is very different
from water! Both carbon dioxide (CO 2 ) and carbon monoxide (CO) consist of carbon and oxygen, but in different
ratios. How do their properties differ?

Types of Compounds

There are different types of compounds. They differ in the nature of the bonds that hold their atoms together. The
type of bonds in a compound determines many of its properties. Three types of bonds are ionic, covalent, and
metallic bonds. You will read about these three types in later lessons. You can also learn more about them by
watching this video: http://www.youtube.com/watch?v=hEFeLYWTKX0 (7:18).