Naming Compounds
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Chemical nomenclature – system for naming compounds
There are there is a different set of naming rules for each 4 different types of
compounds
o Binary molecular (covalent) compounds
o Ionic compounds
o Inorganic acids
o Organic compounds (alkanes and simple alcohols)
Naming binary molecular (covalent) compounds
o A binary molecular (covalent) compound
consists of atoms of 2 different nonmetals
o Name of the element farther to the lower left
of the periodic table is written first
o A prefix is used to show the # of atoms of
each element in the compound
▪ Shown in the table on the right
▪ We only use “mono-“ for the second
element, never the first.
▪ Must have these prefixes
memorized
o the ending of the second element is changed
to -ide.
Prefix
Meaning
mono-
1
di-
2
tri-
3
tetra-
4
penta-
5
hexa-
6
hepta-
7
octa-
8
nona-
9
deca-
10
Chemical Formula
Name
𝑆𝑂2
Sulfur dioxide
PCl5
Phosphorus pentachloride
𝑆𝑖𝐵𝑟4
Silicon tetrabromide
P2O6
Diphosphorus hexoxide
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Naming ionic compounds
o Monoatomic cations (metals)
▪ Same name as the element they are formed from
• This is because these elements always have the same charge
▪ Some metals can form ions with more than 1 charge
• Ex. Cu+, Cu2+
• Elements that can have more than one charge:
o Cu, Co, Fe, Mn, Hg, Ni, Pb, Sn, Cr
• When writing the names of a substance containing one of
these metals, we must specify the charge using Roman
numerals
o Ex. CoCl3 → cobalt (III) chloride
o Ex. Fe(NO3)2 → iron (II) nitrate
o Monoatomic anions (nonmetals)
▪ The name of the element, with the suffix changed to -ide
• Ex. Ca3N2 → calcium nitride
o Polyatomic ions
▪ Do not undergo any changes in their name
▪ Ex. Na2SO4 → sodium sulfate
▪ Must know the names of all polyatomic ions on the list in the page
below:
Chemical Formula of Polyatomic Ion
Name of Polyatomic Ion
𝑁𝐻4+
Ammonium
𝐶𝑁 −
Cyanide
𝑂𝐻 −
Hydroxide
𝐶2 𝐻3 𝑂2−
Acetate
𝐶𝐻3 𝐶𝑂𝑂−
𝑁𝑂2−
Nitrite
𝑁𝑂3−
Nitrate
𝐶𝑙𝑂2−
Chlorite
𝐶𝑙𝑂3−
Chlorate
𝐶𝑙𝑂4−
Perchlorate
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𝑀𝑛𝑂4−
Permanganate
𝐶𝑂32−
Carbonate
𝑆𝑂32−
Sulfite
𝑆𝑂42−
Sulfate
𝑃𝑂43−
Phosphate
Inorganic acids
o Inorganic acid – consists of an anion (mono or polyatomic) and 1+ hydrogen
ions.
o Hydrogen ion – formed when losing its only electron
▪ *hydrogen atoms contain 1p, 1e, and 0n
▪ Often called “protons”
o Inorganic acids must contain enough hydrogen ions to cancel out the charge
of the anion
▪ Ex. HF (hydrogen ion = +1, fluoride ion = -1)
▪ Ex. H3PO4 (3 hydrogen ions = +3, phosphate ion = -3)
o Naming rules for inorganic acids
▪ If the anion of the acid ends in “-ide”, we change the ending to “-ic
acid”, and we add the prefix “hydro-“.
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Example: 𝐻𝐶𝑙 → hydrochloric acid
(anion = chloride)
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Example: 𝐻𝐵𝑟 → hydrobromic acid
(anion = bromide)
If the anion of the acid ends in “-ite”, we change the ending to “-ous
acid”.
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Example: 𝐻𝐶𝑙𝑂2 → chlorous acid (anion = chlorite)
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Exception: 𝐻2 𝑆𝑂3 → sulfurous acid
(anion = sulfite)
If the anion of the acid ends in “-ate”, we change the ending to “-ic
acid”.
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Example: 𝐻𝑁𝑂3 → nitric acid
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Exception: 𝐻2 𝑆𝑂4 → sulfuric acid (anion = sulfate)
(anion = nitrate)