Compounds and Molecules Chapter 22 - notes

I. What are compounds? A. Compound – substance made of atoms of more than one element bound together 1. Properties of the compound are different from those of the component elements

I. What are compounds? 2. Examples  sodium chloride NaCl  made from an alkali metal (soft and shiny), and a halogen (poisonous green gas)

I. What are compounds? B. Chemical bond – the attractive force that holds atoms or ions together  several types – some stronger than others

I. What are compounds? C. A compound always has the same chemical formula 1.Chemical formula – shows the types of elements, and number of atoms of each element in the compound. 2. Compounds always have the same elements in the same proportions

I. What are compounds? 3. Examples: Water  H 2 O 1 oxygen atom 2 hydrogen atoms Hydrogen Peroxide  H 2 O 2 2 hydrogen atoms 2 oxygen atoms

I. What are compounds? D. Chemical structure shows the bonding within a compound 1. Chemical structure – arrangement of bonded atoms or ions in a substance  determines many properties 2. Bonds between any 2 atoms are always straight

II. Models of compounds  helps you “see” a structure A. Ball and stick model 1. The ball represents the atom 2. The stick represents the bond between two atoms

Ball and Stick Model examples

II. Models of compounds B. Structural formula – a drawing representing the structure 1. Chemical symbols represent atoms 2. Lines represent bonds

Structural Formula Models

II. Models of compounds C. Space filling model 1.Shows the actual space occupied by the atoms 2. Examples

Space Filling Model Examples

III. How does structure affect properties? A. Compounds with network structures are strong solids 1. Networks can be made of atoms or ions 2. Network structures have strong bonds 3. Strong bonds = high melting point

Network Structures Examples 2. Examples:

III. How does structure affect properties? B. Compounds can be made of molecules 1. Molecule – smallest unit of a substance, formed of one or more atoms bound together  can be multiple atoms of the same element bound together  oxygen we breathe is O 2

III. How does structure affect properties? 2. Attractions between two molecules is lower than the attractions of the atoms in each molecule 3. Example: C 12 H 22 O 11  table sugar – the atoms are bound together more strongly than any two molecules would be to each other