Molecules, Atoms and Compounds

Element

A substance made up of only one kind of atom.

Examples: Helium, Copper, and Gold

Compound

A substance made up of 2 or more DIFFERENT

elements.

Examples: Copper II oxide, salt (NaCl) and water (H2O)

Element or Compound?

Ca

Na2O

O2

Can be written with

Chemical Symbols

1 or 2 letters used to represent an element

1st letter is always capitalizedIf there is a 2nd letter it is lower

case

Chemical Formulas

Subscripts indicate the number of atoms of the element.

Example: AlCl3

1 aluminum atom3 chlorine atoms

Chemical formulas

Practice:NH4Cl

Mg(OH)2

Pb(NO3)2

Drawing Molecules

represents a molecule made up of 2 different elements

Another way to draw a molecule:

Drawing Molecules

Draw a pictorial representation of the following:

Ca

Calcium Oxygen

O2 CaO

Drawing Practice

H2O

NH3

CCl4