Naming Ionic Compounds
Features of ionic compounds
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Metals give up electrons to form positively charged cations.
Non-metals gain electrons to form negatively charged anions.
Ionic compounds are formed from the attraction between cations and anions. Use the number of each ion so
that the compound is neutral.
When we name an ionic compound, we write
(1) The name of the cation comes first followed by the name of the anion, changing the name of the anion to end
in –ide for monotomic anions. The names of polyatomic anions are not altered.
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NaCl  sodium chloride
ZnI2  zinc iodide
NaNO3  sodium nitrate
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Ag2CO3  silver cabonate
(NH4)2SO4  ammonium sulfate
(2) In those cases where the metal can form cations of differing charges the positive charge is given by a
roman numeral in parentheses
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CuO  copper (II) oxide
Cu2O  copper (I) oxide
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Cr2O3  chromium (III) oxide
CrO3  chromium (VI) oxide
Oxyanions (polyatomic ions with oxygen in them)
Oxyanions are those polyatomic anions containing oxygen. There are a large number of oxyanions, which makes it
difficult to remember all of their names. Fortunately there is a set of rules that makes this task much easier. The
rules for naming oxyanions and the names for the most important oxyanions are given below.
(1) The ending -ate is used for the most common oxyanion of a given element.
 NO3-  Nitrate ion
 PO43-  Phosphate ion
2 SO4  Sulfate ion
 ClO3-  Chlorate ion
 CO32-  Carbonate ion
(2) The ending -ite is used for the oxyanion with the same charge, but one less oxygen than the -ate oxyanion.
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NO2-  Nitrite ion
SO32-  Sulfite ion
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PO33-  Phosphite ion
ClO2-  Chlorite ion
(3) The prefix per- is used if there is an oxyanion with the same charge but one more oxygen than the -ate
oxyanion, while the prefix hypo- is used if there is an oxyanion with the same charge but one less oxygen than the ite oxyanion.
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ClO4-  percholorate ion
ClO3-  chlorate ion
ClO2-  chlorite ion
ClO-  hypochlorite ion
Acids
We constantly encounter acids in everyday life,
from citric acid and ascorbic acid (vitamin C) to
acetic acid (vinegar) and hydrochloric acid. We will
consider acids in more detail in the next two
chapters, but before we can do that we must be
able to name common acids.
A simplistic definition of an acid is a compound
that dissolves in water to release H+ ions. The most
common acids are those which result when we add
enough H+ ions to an oxyanion to balance its charge.
The rules for naming simple acids are based on the
names of the anions, they are given below.
(1) When the anion ends in -ide, change the ending to -ic and add the prefix hydro- for the name of the acid.
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Anion = chloride (Cl-)  hydrochloric acid (HCl)
Anion = bromide (Br-)  hydrobromic acid (HBr)
Anion = sulfide (S2-)  hydrosulfuric acid (H2S)
(2) When the anion ends in -ate, change the ending to -ic for the name of the acid.
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Anion = chlorate (ClO3-)  chloric acid (HClO3)
Anion = sulfate (SO42-)  sulfuric acid (H2SO4)
Anion = nitrate (NO3-)  nitric acid (HNO3)
(3) When the anion ends in -ite, change the ending to -ous for the name of the acid.
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Anion = phosphite (PO33-)  Phosphorous acid (H3PO3)
Anion = chlorite (ClO2-)  Chlorous acid (HClO2)
Anion = hypochlorite (ClO-)  Hypochlorous acid (HClO)
Features of covalent compounds
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Two or more Nonmetals SHARE electrons to fill their electron orbitals with a full shell.
When we name formulas of covalent compounds:
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Use the prefix system for indicating the number of each element in the compound.
Never use the prefix “mono-” for the first element.
The least electronegative elements is written first.
mono3. tri5. penta7. heptadi4. tetra6. hexa8. octa-
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P2O5 – diphosphorous pentoxide
CO – carbon monoxide
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N2O – dinitrogen monoxide
Cl2O7 – dichlorine heptoxide
9. nona10. deca-