naming ionic compounds


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Naming an ionic compound :

The name of an ionic compound consists of two words .The first word names the cation and second names the anion.This is of course the same order on which the ions appear in the formula.


Monoatomic cations take the name of the metal from which they are derived . For example ; Na+ sodium K+ potassium .


However, there is one complication . Certain metals in the transition and post transition series form more than on e cation , for example : Fe2+ and Fe3+  .To distinguish between these cations , the charge must be indicated in the name . This is done by putting charge as a Roman numeral in the parentheses after the name of the metal :


   Fe2+    iron(II)   and     Fe3+   iron (III)


An older system also uses suffixes - ic for the ion of higher charge and -ous for the ion of lower charge .These were added to the stem of the latin name of the metal , so that Fe2+ ion was referred to as ferrous and the Fe3+  ions was reffered as ferric .


Monoatomic anions are named by adding the suffix - ide to the stem of the name of the nonmetal from which they are derived.


N3-   nitride , O2-  oxide , F -  flouride , H -  hydride


The polyatomic ions (check out the download for the polyatomic ion table) are given special names.Certain polyatomuc ion containing oxygen (oxoanions) .The names of several such oxoanions are shown in table 2.3 . From the entries in the table, you should be able to deduce the following rules:


1) Whe a non metal forms two oxoanions, the suffix -ate is used for the anion with the larger number of oxygen atoms. The suffix -ite is used for the anion containing fewer oxygen atoms.


ClO- hypochloraite ion  and ClO2- chlorite ion


2) When a non metal forms more than two oxoanions, the prefixes per - ( largest number of oxygen atoms) and hypo - ( fewest oxygen atoms) are used as well.


ClO3- chlorate ion  and ClO4-  perchlorate ion


Naming of the ionic compound consists of two words : the first word names the cation and the second names the anion .This is ofcourse , the same order in which the ions appear in the formula.


In naming the compounds of transitiion and post transition metals , we ordinarily indicate the charge of the metal cation by a Roman numeral:


Cr(NO3)3  chromium (III) nitrate   SnCl2 tin (II) chloride


in contrast we never use Roman numberals with compounds of group I and II they always form cations with charges of +1 and +2 respectively.

CaS  - calcium sulfide