Chemical Nomenclature

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Chemical Nomenclature
Chemical Nomenclature as we know it is born with
the publication of Méthode de nomenclature
chimique by Antoine-Laurent Lavoisier,
Claude-Louis Berthellot, Antoine de Fourcroy,
and Guyton de Morveau. The names proposed were
based on the elements origin or function. (Image
produced courtesy of the Library Information
Centre, Royal Society of Chemistry)
http//www.rsc.org/chemsoc/timeline//pages/1787.ht
ml
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Chemical Nomenclature

• System of rules for naming pure substances
• Elements element name used even if the
  substance is di- or polyatomic
• O2 oxygen S8 sulfur
• Compounds - naming differs depending on whether a
  substance is held together primarily by ionic or
  covalent bonds.

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Ions

• Electrons are arranged on levels or shells.
  Atoms are most stable with 8 electrons on their
  outermost shell. This is often referred to as
  the octet rule.
• Number of electrons on the outer shell Group
  number for elements in Groups I-VIII A (using the
  US convention labeling on periodic table)

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Figure 2.10
The modern periodic table.
US Convention
IUPAC Convention
Silberberg, Principles of Chemistry
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Ions

• To achieve the octet, atoms with more than 4
  electrons on the outer shell will gain enough
  electrons to reach 8.
• Cl Group 7 7 electrons on outer
  shell
• Cl will gain 1 e- .
• Now e- 18 but p 17 so the chlorine is an
  ion with the formula Cl1-.

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Ions

• O Group 6 6 electrons on outer shell
  O will gain 2 e- .
• Now e- 10 but p 8 so the oxygen is an ion
  with the formula O2-.
• P Group 5 5 electrons on outer shell
• P will gain 3 e-
• Now e- 18 but p 15 so the phosphorus is an
  ion with the formula P3-

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Ions

• Na Group 1 1 electron on outer shell O
  will lose 1 e- to expose the complete inside
  shell.
• Now e- 10 but p 11 so the sodium is an ion
  with the formula Na1.
• Mg Group 2 2 electrons on outer shell
• Mg will lose 2 e-
• Now e- 10 but p 12 so the magnesium is an
  ion with the formula Mg2

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--
1
--
2
3
1-
2-
3-
Generally metals form cations and non-metals form
anions.
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Binary Ionic Compounds

• Cations (positively charged ions) and anions
  (negatively charged ions) will associate with
  each other and form a neutral binary compound to
  reduce energy .
• 1 Na 1 Cl- NaCl
• 1 Ca2 1 O2- CaO
• 3 K 1 N3- K3N
• 2 Al3 3 S2- Al2S3

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Naming binary ionic compounds
The name of the cation (positively charged ion)
is written first, followed by that of the anion.
The name of the cation is the same as the name of
the metal.
Many metal names end in -ium.
The name of the anion (negatively charged ion)
takes the root of the nonmetal name and adds the
suffix -ide.
Calcium and oxygen form calcium oxide. Aluminum
and sulfur form aluminum sulfide.
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Naming Ionic Binary Compounds
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Naming Binary Ionic Compounds
(a) magnesium and nitrogen
(b) iodine and cadmium
(c) strontium and fluorine
(d) sulfur and potassium
PLAN
Use the periodic table to decide which element is
the metal and which the nonmetal. The metal
(cation) is named first and we use the -ide
suffix on the nonmetal name root.
SOLUTION
(a) magnesium nitride
(b) cadmium iodide
(c) strontium fluoride
(d) potassium sulfide
From Silberberg, Principles of Chemistry
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Determining Formulas of Binary Ionic Compounds
PLAN
Compounds are neutral. We find the smallest
number of each ion which will produce a neutral
formula. Place subscripts to the right of the
element symbol.
SOLUTION
(a) Mg2 and N3- three Mg2(6) and two N3-(6-)
Mg3N2
(b) Cd2 and I- one Cd2(2) and two I-(2-)
CdI2
(c) Sr2 and F- one Sr2(2) and two F-(2-)
SrF2
(d) K and S2- two K(2) and one S2- (2-) K2S
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Binary Ionic Compounds

• The B group elements may form cations with more
  than one charge.
• To specify which cation forms a compound, a roman
  numeral equal to the charge is added to the
  cation name.
• Fe2 iron (II) Fe3 iron (III)

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Sample Problem 2.7
Determining Names and Formulas of Ionic Compounds
of Elements That Form More Than One Ion
PLAN
Compounds are neutral. We find the smallest
number of each ion which will produce a neutral
formula. Use subscripts to the right of the
element symbol.
SOLUTION
(a) Tin (II) is Sn2 fluoride is F- so the
formula is SnF2.
(b) The anion I is iodide(I-) 3I- means that
Cr(chromium) is 3. CrI3 is chromium(III) iodide
(c) Manganese (IV) is Mn2 oxide is S2-,
therefore the formula is MnS2.
(d) Cr is chromium the anion O is oxide(2-)
the compound is cobalt (VI) oxide.
Modified from Silberberg, Principles of Chemistry
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Polyatomic Ions

• Some atoms form bonds that hold atoms together in
  a structure that has an overall charge (rather
  than as a neutral compound. These ions are
  called polyatomic ions.
• CO32- carbonate SO42- sulfate
• Compounds with polyatomic ions are named with the
  cation and anion name.
• Na2SO4 sodium sulfate

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Determining Names and Formulas of Ionic Compounds
Containing Polyatomic Ions
(a) Fe(ClO4)2
(b) sodium sulfite
PLAN
Note that polyatomic ions have an overall charge
so when writing a formula with more than one
polyatomic unit, place the ion in a set of
parentheses.
SOLUTION
(a) ClO4- is perchlorate iron must have a 2
charge. This is iron(II) perchlorate.
(b) The anion sulfite is SO32- therefore you
need 2 sodiums per sulfite. The formula is
Na2SO3.
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Hydrates

• Some compounds have water molecules attached as
  part of their structure. These are termed
  hydrates.
• CuSO4. 5H2O
• copper (II) sulfate pentahydrate

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Binary Acids

• When certain binary gases dissolve in water they
  form acids with the same formula. The name is
  changed to add ic acid to the anion
• HCl (g) ? HCl (aq)
• hydrogen chloride hydrochloric acid

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Binary Acids

• HF (aq) hydrofluoric acid
• HCl (aq) hydrochloric acid
• HBr (aq) hydrobromic acid
• HI (aq) hydroiodic acid
• HCN (aq) hydrocyanic acid

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Oxyacids

• Acids containing oxygen most do not exist in the
  same form without water
• HNO3 nitric acid
• HNO2 nitrous acid
• H2SO4 sulfuric acid
• H2CO3 carbonic acid
• H3PO4 phosphoric acid
• HC2H3O2 or CH3COOH acetic acid

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Covalent Binary Compounds

• Non-metals form bonds by sharing electrons rather
  than transferring them.
• The resulting bond is referred to as a covalent
  bond.
• The element farthest to the left or lower on the
  periodic table is generally written first.
  Subscripts are replaced by numerical prefixes in
  the name.

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Covalent Binary Compounds

• CO2 carbon dioxide
• N2O dinitrogen oxide
• P2S5 diphosphorus pentasulfide
• SiCl4 silicon tetrachloride
• For compounds where two vowels occur together
  when the prefix is added, the vowel from the
  prefix can be dropped (except for iodine).
• N2O5 dinitrogen pentaoxide

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Naming Binary Covalent Compounds
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Determining Names and Formulas of Binary Covalent
Compounds
(a) What is the formula of carbon disulfide?
(b) What is the name of PCl5?
(a) Carbon is C, sulfide is sulfur S and
di-means 2 - CS2.
(b) P is phosphorus, Cl is chloride, the prefix
for 5 is penta-. Phosphorus pentachloride.
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