Rules for Naming Compounds

Compounds are formed from two or more different atoms bonded together. These compounds are represented by formulas that use the element symbols and subscripts to indicate how many of each element is present in the compound. (H2O contains 2 atoms of Hydrogen and l of oxygen.  NH3 contains l atom of nitrogen and 3 atoms of hydrogen.) There are two types of formulas:  Ionic and Covalent.  Each of these are named in a slightly different way. 

Ionic compounds consist of  metals (+ cations) attached to nonmetals (-anions) . Many of these contain radical groups (polyatomic  ions or groups of atoms with a charge) Molecular (Covalent) consist of a nnonmetal element bonded to other nonmetals.

Nomenclature: The naming of compounds.

Ionic
First name is the name of the element written first or  NH4+ (ammonium)

Last name is the name of the element written last but with an ide ending
(sulfur becomes sulfide, bromine becomes bromide, fluorine becomes fluoride, oxygen becomes oxide etc) or if a group is written last, use the group’s name.

Middle names are only necessary when the cation (positive ion)  has more than one oxidation

state (charge).   The middle name is the charge not the number of atoms. It is mainly the transitional elements

that will need to have a middle name.

Fe +2             iron (II)

Co +3             cobalt (III)

Sn +4             tin (IV) 


Examples        First name                  Last name

NaCl               sodium                       chloride

K2S                potassium                   sulfide

CaBr2             calcium                       bromide

Na2CO3         sodium                       carbonate (group name)

KNO3             potassium                  nitrate (group name)

(NH4)2 S         ammonium (group)    sulfide

FeO                iron (II)                      oxide                


Molecular (Covalent):

First name is the name of the element written first.

Last name is the name of the element written last but with an ide ending

BOTH NAMES  USE PREFIXES TO TELL THE NUMBER OF EACH ELEMENT.

Prefixes:    mono-1      di - 2      tri - 3      tetra- 4   penta-5     hexa-6

Examples       First name         Last Name

CO                carbon              monoxide

CO2              carbon              dioxide

N2O4           dinitrogen          tetraoxide

SF6               sulfur                hexafluoride

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