Topic 6: Chemical Compounds When two or more elements bond together they form compounds. There are two types of compounds molecular and ionic. Molecular Compounds A non – metal with a non – metal do not form ions in a solution usually does not conduct electricity solid, liquid or gas at room temp. low melting and boiling points because attraction between molecules is weak.

Naming Molecular Compounds Use a prefix to indicate how many atoms of the 1st element are present. 2 = di, 3 = tri, 4 = tetra, 5 = penta, 6 = hexa, 7 = hepta, 8 = octa, 9 = nona Do not use a prefix for 1. Write the name of the 1st element. Use the same prefixes for the number of atoms of the second element. (mono now will be used for 1) Write the name of the second element except change the ending to “ide” Example: What are the names of the following molecular compounds? CO CCl4 Si2O2 C3H8

Determining Molecular Chemical Formulas Write the symbol of the first element. Use a subscript number on the first element based on the prefix. If no prefix a one or no number is acceptable. Write the symbol of the second element. Use a subscript number on the second element based on the prefix. If mono is used a one or no number is acceptable. Do not write a state/phase symbol unless provided with one.

Example: Write the chemical formulas for the following molecular compounds. carbon dioxide Liquid heptaboron disillicide sulfur tetrachloride Gaseous triphosphorous monoxide

Special Cases: Diatomics These are molecular compounds that are made of two atoms from the exact same element, O2, N2, H2. Halogens are diatomic! These elements are not named the same way as others they are simply called by the elements original name. O2 = oxygen N2 = nitrogen H2 = hydrogen