HOW TO NAME CHEMICAL COMPOUNDS
DIRECTIONS: If the answer to a question is No, go to the next similarly numbered or lettered question. If the answer is Yes, follow any directions listed and go on to the first subdivision. Once you have said Yes to a subdivision, all following subdivisions of that question are skipped. In this manner continue through questions 1 ---> 6 until the compound has been named.
Is the first element a nonmetal?
Is the compound binary (consists of only two elements) ?
Is the first element H?
Is the compound a gas?
Write hydrogen as the first part of its name.
[Go to #3}.
The compound is a binary acid
Write the prefix "hydro", follow this by the root of the name for the second element, end the first word of the compound name in "ic". Follow this with the word "acid".
Example: HCl(aq) = hydrochloric acid.
Is the second element H?
Some common examples:
This is usual type of binary compound compound composed of two nonmetals.
Such a compound is named by using a Greek prefix designating the number of atoms for the elements in the formula. Note that the Greek prefix "mono-" is not used with the first element, just the second. Also, end the name of the second element in "ide".
Greek Prefixes Number
For Example: CO = carbon monoxide, P2O5 = diphosphorus pentoxide, CCl4= carbon tetrachloride.
Is the positive ion NH4+?
Write ammonium for the first part of the compound name.
[Go to #3}
Is the first element H?
Find the name of the negative ion.
Does the name of the negative ion end in "-ide"?
Is the compound a gas?
Write 'hydrogen" followed by the name of the negative ion.
For example: HCN (g) = hydrogen cyanide
Is the compound an aqueous solution?
Change the "-ate" ending of the negative ion to "-ic", add the prefix "hydro-" to the negative ion, and add the word "acid" to the compound name.
For example: HCN (aq) = hydrocyanic acid
Does the name of the negative ion end in "-ate'?
Change the "-ate" ending of the negative ion to "-ic", and add the word "acid".
For example: H3BO3 = boric acid (BO33- = borate)
Does the name of the negative ion end in "-ite'?
Change the "-ite" ending of the negative ion to "-ous", and add the word "acid".
For example: HNO2 = nitrous acid (NO21- = nitrite)
Is the first element a metal?
Does the first element have a varying oxidation number? (See table 3)
Write the name of the first element followed by its oxidation number (omitting the +) written as a Roman Numeral in ( ).
To determine this oxidation number: (1) multiply the oxidation number of the negative ion (anion) in the formula by the number of these negative ions, (2) divide this product by the number of atoms of the first element in the formula and (3) change the sign to +. (Remember the sum of the oxidation numbers in a compound must be equal to zero; the sum of the oxidation numbers in a polyatomic ion must equal the charge on the ion.)
For example: Fe2(SO4)3 = iron(III) .....
Write the root of the name for the first element followed by "ous" for the lower of the two oxidation numbers or "ic" for the higher of the two oxidation numbers.
For example: Fe2(SO4)3 = ferric ..... because the two oxidation numbers for iron are +2 and +3.
Write the name of the first element.
Is the the negative ion in the compound formula a single element?
For the second part of the compound name, write the name of the element, changing the ending to "-ide".
For example: The chlorine in Cl- becomes chloride.
Is the first element of the negative ion in the compound formula H?
Is the oxidation number of the polyatomic ion following the hydrogen equal to -2?
Add the prefix "bi-" to the name of this ion and write it as the second part of the formula name.
OR Write the word "hydrogen" followed by the name of that polyatomic ion.
For example: the HSO41- ion is called bisulfate or hydrogen sulfate; NaHSO4 is called sodium bisulfate or sodium hydrogen sulfate.
To write the second part of the compound name: (1) add the Greek prefix for the number of hydrogen to the word "hydrogen" and (2) follow this by the name of the polyatomic ion written after the H in the negative ion of the formula.
For example: Na2HPO4 is sodium monohydrogen phosphate and NaH2PO4 is sodium dihydrogen phosphate.
Write the name of the negative ion as the second part of the compound name.
Is the compound a hydrate? (Is there an . X H2O written at the end of the formula?)
After the name of the first part of the formula write the word "hydrate" with the appropriate Greek prefix to indicate the number of water molecules in the hydrated form.
For example: CuSO4. 5 H2O is copper(II) sulfate pentahydrate.
Copyright © 1996 by Jan Hildenbrandt