Chapter 2-1

A substance made up of two or more different types of atoms bonded together.

Elements are to compounds as letters are to words.

Elements change when they form compounds. Sounds of letters change to form words

All compounds have the same ratio of elements. Ammonia: 3 hydrogen for every nitrogen

Ratio of 3:1 Hydrazoic acid: 1 hydrogen for 3 nitrogen

atoms Ratio of 1:3

Different ratios = different properties

A chemical formula uses chemical symbols and the ratios of elements to represent a compound.

Carbon Dioxide: 1 carbon and 2 oxygen Symbol for Carbon

C Symbol for Oxygen

O CO2

Subscript: Number to the lower right, tells the number of atoms

Hydrogen Chloride: 1 hydrogen and 1 chlorine

Water: 2 Hydrogen and 1 Oxygen Ammonia: 1 Nitrogen and 3 Hydrogen CH4

C3H8

Hydrogen Chloride: 1 hydrogen and 1 chlorine

HCl

Water: 2 Hydrogen and 1 Oxygen H2O

Ammonia: 1 Nitrogen and 3 Hydrogen NH3

CH4

Methane: 1 Carbon and 4 Hydrogen

C3H8 Propane: 3 Carbon and 8 Hydrogen

Page 45 numbers 1, 2, 4 and 6.