Sec 2.8: Naming Inorganic Compounds
Major divisions of compounds:
Organic: contain C, with H, O, N, S, halogens
Inorganic: All others
Here’s a nice visual way to remember this…..
Naming ionic compounds
Rules:
cation is always named and listed first
anion named and written last
How to name cations and ions?
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Naming monoatomic cations
e.g., Na+, Ca2+, Al+3 : ion derived from a single atom
cation takes the name of the element itself, e.g.,
sodium ion, aluminum ion, etc.
H+ is called hydrogen ion and also a proton – why?
Some atoms can form more than one cation, e.g.,
Fe: Fe2+, Fe3+
Cu: Cu+, Cu2+
Transition metal atoms are notable for doing this!!
To name transition metal cations: use Roman
numeral notation for charge, e.g., iron (II), iron
(III), copper (I)
e.g., What is the name of the cation in FeBr3?
What about Fe2O3?
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Cations formed from nonmetals
-have names that end in -ium
only 2 common ones
NH4+ ammonium ion
H3O+ hydronium ion
Notice that mercury (Hg) forms two cations, Hg2+ and
Hg22+. How do these differ???
Please study table 2.4, p. 60, Common cations!
Naming monoatomic anions
Monoatomic anion: derived from a single atom
e.g., O2-, F-, S2commonly come from nonmetallic elements
named by dropping ending of element name and
adding –ide
e.g., name the anions: F-, O2-, P389
Polyatomic anions: table 2.5
Know the names, formulas & charges for the ions in table
2.5
Note that a number of the polyatomic anions in Table 2.5
contain oxygen
These species are known as oxyanions – notice that their
names end in either – ate or –ite (contrast to the earlier- ide
suffix)
The most common oxyanions are
CH3COO-
acetate ion
CO32-
carbonate ion
NO3-
nitrate ion
SO42-
sulfate ion
PO43-
phosphate ion
ClO4-
perchlorate ion
OH-
hydroxide ion
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Notice that some elements, e.g., nitrogen, sulfur, and
chlorine, form more than one oxyanion
How to name these species?
When an element forms only two oxyanions, the one that
contains the most oxygens ends in -ate, the one with
fewer oxygens ends in –ite
e.g., Name the following pairs of anions
NO2-, NO3SO32-, SO42-
What about the halide oxyanions? Cl, Br, and I form a
series of four oxyanions, all with -1 charges:
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Now we can combine the names of cations and anions and
name and write the formulas for ionic compounds:
E.g., name the following compounds:
Fe2O3
Ba(OH)2
Li3PO4
Cr2(CO3)3
NaClO
Sr(CH3COO)2
NH4NO3
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And we need to be able to go backwards, i.e., from name
to formula:
e.g., write the chemical formula for:
zinc (II) acetate
sodium perchlorate
barium bromate
iron (III) carbonate
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Naming Acids
Acids are compounds which donate H+ ions in water
Acids are typically written with H as the first element,
e.g. HCl, H2SO4
the formula of an acid consists of an anion whose
charge is balanced by one or more H+ ions, e.g.,
anion
acid
Cl-
HCl
PO43-
H3PO4
Acids are named based on the identity of the
anion within the acid!
Acids whose anions end in -ide have names with the
hydro- prefix and -ic acid ending
e.g., HF, H2S
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Acids whose anions end in -ate are given an -ic acid ending
e.g., HNO3, H2SO4
Acids whose anions end in -ite are given an -ous acid
ending
e.g., HNO2, H2SO3
What about anions derived from
adding H+ to an oxyanion, e.g.
HCO3- or H2PO4-?
Naming molecular compounds
Procedure for naming binary molecular compounds is
similar to that for naming ionic compounds
Element furthest left is usually written and named first
If both elements in same group, lower one is named
first
Name of second element given the –ide ending
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However: we cannot predict the formulas for most
molecular substances as we did for ionic substances
A pair of elements can often form several different
molecular compounds, e.g., N and O:
NO, NO2, N2O3, N2O4
To distinguish these compounds from one another, we
use prefixes to denote the numbers of atoms of each
element present:
NO
nitrogen monoxide
NO2
nitrogen dioxide
N2O3
dinitrogen trioxide
N2O4
dinitrogen tetroxide
e.g., name the following compounds:
PCl5
SiBr4
Cl2O
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Naming Simple Organic Compounds
Hydrocarbon: compound that contains only C and H
If the compound contains only single C-H and C-C
bonds, it is called an alkane
Alkanes are named based on how many C atoms they
contain, and their names end in –ane
Prefixes are a little different than for other molecular
compounds…….
# C atoms
prefix
1
meth-
2
eth-
3
prop-
4
but-
at 5 C atoms we again use pent-, hex-, hept, etc.
E.g. write the chemical and structural formulas for
methane, ethane, and propane (C forms 4 bonds!!)
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Problems du Jour
Name the following acids:
H2CO3
H2S
CH3COOH (or HC2H3O2)
H2SO3
HBrO3
HNO2
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Problems du Jour
Write chemical formulas for the following:
chlorous acid
calcium hydrogen carbonate
sodium dihydrogen phosphate
calcium monohydrogen sulfide
octane
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