Naming Compounds

Just like a family tree, the main trunk expands to give way to branches which divide even more to reveal connections of kinship.

We will use the same philosophy to aid in the naming of binary compounds. “Climb” or follow the branches as they lead to you to identify the type of compound you have. Then use the corresponding naming rule to name the compound. Follow these guidelines or you may find yourself out on a limb!

Begin with asking: Is this compound ionic or molecular in nature? Then follow that branch to find subcategories stem from it.

Recall that ionic compounds are easily identified by a metal + nonmetal pairing while molecular compounds contain two nonmetals (including those pesky polyatomic ions).

1. Ionic: Metal + Nonmetal
   1. Binary Compounds Using Main Group Metals: Give the name of the first element (cation) followed by the stem of the second element (anion) plus the suffix “ide.”
      1. Ex. NaCl: Sodium + chlor + ide= Sodium Chloride
   2. Binary Compounds Using Transition (Variable Charge) Metals: Give the name of the first element (cation) followed by the charge in Roman Numerals in parathesese then the stem of the second element (anion) plus the suffix “ide.”
      1. Ex. FeO: Iron (II) Oxide
   3. Using Polyatomic Ions: For Main Group metals, name the metal followed by the name of the polyatomic ion. For Transition Metals, the rules in section c apply: so give the name of the first element (cation) followed by the charge in Roman Numerals in parathesese then the name of the polyatomic ion.
      1. Ex. NaOH: Sodium Hydroxide AlPO₄ : Aluminum Phosphate
2. Molecular: Nonmetal + Nonmetal
   1. Binary Compounds: Give the number of atoms of the first nonmetal using Greek prefixes followed by the name of the first nonmetal plus the number of atoms of the second nonmetal in Greek prefixes followed by the stem of the second nonmetal plus the suffix “ide.”
      1. Exception: For the FIRST nonmetal only, it is not necessary to note “mono” to indicate that there is only one atom; for the second nonmetal, however, you should.
      2. Greek Prefixes:
         

         Mono 1	Tetra 4	Hepta 7	Deca 10
         Di 2	Penta 5	Octa 8
         Tri 3	Hexa 6	Nano 9

         Ex. N₂O₄ : Dinitrogen tetraoxide (di + nitrogen + tetra+ ox + ide)

3. Acids
Name the compound as a molecular compound. Then use the following guide to change it to its acidic name:

Examples:

HCl: hydrochloric acid (hydro + chlo + ic + acid)

HClO₃: chloric acid (chlor + ic + acid)

HClO: hypochlorous acid (hypochlor + ous + acid)

IV. Hydrates

Name the compound using the appropriate naming rules then add the Greek prefix to indicate the number of water molecules, then the word “hydrate.”

Examples: NaCl ● 5H₂O : sodium chloride pentahydrate

Practice Exercises and Answers: Write the names of the following formulas:

Ionic Compounds:

Ca3(PO4)2 = _________________	BaCl2 = ________________
Al2(SO4)3 = __________________	FeO =________________
NaC2H3O2 = _________________	SnCl-4 = ________________

Molecular Compounds:

PCl5 = ___________________	CO2=  _________________
H2-O = ___________________	N2Cl4= _________________
HNO3= __________________	H2SO3= _________________

Answers:

Ionic Compounds:

Calcium phosphate	barium chloride
Aluminum sulfate	iron (II) oxide
Sodium acetate	Tin (IV) chloride

Molecular Compounds:

Phosphorus pentachloride	carbon dioxide
Dihydrogen monoxide	dinitrogen tetrachloride
nitric acid	sulfurous acid