Molecules, Atoms and Compounds

A substance made up of only one kind of atom. Element A substance made up of only one kind of atom. Examples: Helium, Copper, and Gold

A substance made up of 2 or more DIFFERENT elements. 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 capitalized If there is a 2nd letter it is lower case

Subscripts indicate the number of atoms of the element. Chemical Formulas Subscripts indicate the number of atoms of the element. Example: AlCl3 1 aluminum atom 3 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:

Draw a pictorial representation of the following: Drawing Molecules Draw a pictorial representation of the following: Oxygen Calcium Ca O2 CaO

Drawing Practice H2O NH3 CCl4