24th February '09

Binary Covalent Nomenclature Tutorial

1) Binary covalent compounds are pure substances that consist of two nonmetallic elements.

2) The water, H2O, you boil to cook your potatoes and the methane, CH4, in natural gas that can be burned to heat the water are examples of binary covalent compounds.

3) MEMORIZED NAMES:

water - H2O
ammonia - NH3
methane - CH4
ethane - C2H6
propane - C3H8

4) The general pattern of such formulas is AaBb, where “A” and “B” represent symbols for nonmetals.

eg. nitrogen and oxygen are nonmetallic elements, the formula N2O3 represents a binary covalent compound.

5) Follow these steps to write the names for binary covalent compounds.

If the subscript for the first element is greater than one, indicate the identity of the subscript using one of the prefixes listed below . We do not write mono- at the beginning of a compound’s name.
Example: We start the name for N2O3 with di-.

Attach the selected prefix to the name of the first element in the formula. If no prefix is to be used, begin with the name of the first element.
Example: We indicate the N2 portion of N2O3 with dinitrogen.
www.
Select a prefix to identify the subscript for the second element (even if its subscript is understood to be one). Leave the "a" off the end of the prefixes that end in "a" and the “o” off of mono‑ if they are placed in front of an element whose name begins with a vowel (oxygen or iodine).
Example: The name of N2O3 grows to dinitrogen tri-.

Write the root of the name of the second element in the formula as shown below.
Example: The name of N2O3 becomes dinitrogen triox-.

Add -ide to the end of the name.
Example: The name of N2O3 is dinitrogen trioxide.

6) Prefixes:

1 - mon(o)
2 - di
3 - tri
4 - tetr(a)
5 - pent(a)
6 - hex(a)
7 - hept(a)
8 - oct(a)
9 - non(a)
10 - dec(a)

Cation Names and Formulas

1) The names of monatomic cations always start with the name of the metal, sometimes followed by a Roman numeral to indicate the charge of the ion.

eg Cu+ is copper(I), and Cu2+ is copper(II).