1. Chapter 6: The Structure of Matter

2. Section 1: Compounds and Molecules

3. Key Ideas What holds a compound together?
How can the structure of chemicals compounds be shown?
What determines the properties of a compound?

4. Key Terms
Chemical bonds
Chemical structure
Bond length
Bond angle

5. Chemical Bonds
The forces that hold atoms or ions together in a compound are called chemical bonds

6. Chemical Structure
Chemical structure is the way the compound’s atoms are bonded to make compound
Just as the structure of buildings can be represented by blueprints, the structure of chemical compounds can be shown by various models

7. Chemical Structure Ball-and-stick model
Represents bond lengths and angles
Bond length is the distance between the nuclei of two bonded atoms
Bond angle is the angle formed by two bonds to the same atom, tells which way these atoms point.

8. Chemical Structure
Ball-and-stick model

9. Chemical Structure Space-filling models
This model shows the space that atoms take up

10. Chemical Structure
Bonds can bend, stretch, and rotate without breaking

11. How Does Structure Affect Properties?
The chemical structure of a compound determines the properties of that compound
Compounds with network structures are strong solids like quartz, made of silicon dioxide, SiO2

12. How Does Structure Affect Properties?
The chemical structure of a compound determines the properties of that compound
Some networks are made of bonded ions like table salt (sodium chloride), that are found in the form of regularly shaped crystals

13. How Does Structure Affect Properties?
The chemical structure of a compound determines the properties of that compound
Some compounds are made of molecules like sugar (C12H22O11), that is made of carbon, hydrogen, and oxygen atoms that are joined by bonds

14. How Does Structure Affect Properties?
The strength of attractions between molecules varies
Compound
State (25oC)
Melting Point (oC)
Boiling Point (oC)
Sugar, C12H22O11
Solid -
Water, H2O
Liquid
100
Dihydrogen Sulfide, H2S
Gas
-86
-61

15. Homework
Classify the following substances as mixtures or compounds: air, CO, SnF2, pure water.
Draw a ball-and-stick model of boron trifluoride, BF3, molecule. In this molecule, a boron atom is attached to three fluorine atoms. Each F-B-F bond angle is 120o, and all B-F bonds are the same length.
Explain why glass, which is made of mostly SiO2, is often used to make cookware.