4. Naming Molecular Compounds

Binary molecular compounds are named using a system of prefixes which indicate the number of first atoms in the compound. The second atom in the formula gets an -ide ending. The prefix mono is used on the second atom only. 

NumberPrefixNumberPrefix
1 mono 6 hexa
2 di 7 hepta
3 tri 8 octa
4 tetra 9 nona
5 penta 10 deca
Ex. CCl4: carbon tetrachloride
As2O3: diarsenic trioxide 
H2O: dihydrogen monoxide (water)

Non-binary molecular compounds, mostly organic, has a different system of nomenclature.

  • Write out the symbol of the elements in the compound. 
  • The first element keeps its name, the second element ends with -ide. 
    Ex. NF3: Nitrogen trifluoride 

Molecular compounds are composed of non-metals. The atoms within molecules are held together by covalent bonds where atoms share electrons. 

The chemical formula for a molecular compound represents the actual number of atoms that form the molecule. For instance, CO2 contains 1 atom of carbon and 2 atoms of oxygen. A covalent on is the attraction of two nuclei for a pair or pairs electrons that they share.
If one pair of election is shared, a single covalent bond is formed. If two pairs of electrons are shared, then a double covalent bond is formed. 

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