1. Chemical Nomenclature
Introduction to
Chemical Nomenclature
Honors Chemistry
Chang: Chapter 2

2. Periodic Table of the Elements
Alkali Earth Metal
Noble Gas
Halogen
Alkali Metal
Group
Period
2.4

3. A diatomic molecule contains only two atoms
A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical forces H2
H2O
NH3
CH4
A diatomic molecule contains only two atoms
H2, N2, O2, Br2, HCl, CO
A polyatomic molecule contains more than two atoms
O3, H2O, NH3, CH4
2.5

4. 2.6

5. An empirical formula shows the simplest
A molecular formula shows the exact number of atoms of each element in the smallest unit of a substance
An empirical formula shows the simplest
whole-number ratio of the atoms in a substance
H2O
molecular
empirical
H2O
C6H12O6
CH2O O3 O
N2H4
NH2
2.6

6. cation – ion with a positive charge
An ion is an atom, or group of atoms, that has a net positive or negative charge.
cation – ion with a positive charge
If a neutral atom loses one or more electrons
it becomes a cation. Na
11 protons
11 electrons
Na+
11 protons
10 electrons
anion – ion with a negative charge
If a neutral atom gains one or more electrons
it becomes an anion.
Cl-
17 protons
18 electrons Cl
17 protons
17 electrons
2.5

7. The ionic compound NaCl
ionic compounds consist of a combination of cations and an anions
the formula is always the same as the empirical formula
the sum of the charges on the cation(s) and anion(s) in each formula unit must equal zero
The ionic compound NaCl
2.6

8. A monatomic ion contains only one atom
Na+, Cl-, Ca2+, O2-, Al3+, N3-
A polyatomic ion contains more than one atom
OH-, CN-, NH4+, NO3-
2.5

9. Chemistry Nomenclature

10. There are over 20 million chemical
compounds known to scientists.
Luckily, we don’t have to memorize
all of them. We can follow the rules
of chemical nomenclature to name
them on sight (usually).

11. Two naming systems: Inorganic compounds: all non-organic compounds.
Organic compounds: contain carbon,
usually in combination with H, O, N
and S. These account for >90% of
chemical compounds.

12. A few carbon-containing compounds
are considered to be inorganic
compounds, and are named using
inorganic nomenclature:
CO, carbon monoxide
CO2, carbon dioxide
CS2, carbon disulfide
carbon compounds containing
CN−, CO32−, and HCO3−

13. Inorganic Compounds There are 4 categories of inorganic compounds:
1. ionic
2. molecular
3. acids and bases
4. hydrates

14. Binary Ionic Compounds
Binary: compounds formed from two
elements
1. The name of the element with a
positive charge is first, followed
by the element with the negative
charge.
2. The metal always precedes the
symbol for the nonmetal.

15. 3. The name of the metal is followed
by the name of the nonmetal
with the suffix –ide added.
4. Ionic compounds are made by
combining anions and cations. The
total positive charge must equal
the total negative charge.

16. -ide derivatives of nonmetals
F – fluoride N - nitride
Cl – chloride P - phosphide
Br – bromide As - arsenide
I – iodide C - carbide
O – oxide Se - selenide
S – sulfide Te - telluride

17. 5. Certain metals, especially transition
metals, can form more than one
type of cation. To differentiate
between each ionic form, use Roman
numerals after the metal ion for
clarification. This method of
labeling metal cations is called the
“Stock System” of nomenclature.

18. An older nomenclature system that is
still in limited use assigns the
-ous ending to the cation with a
lower positive charge, and the
-ic ending to the cation with a
higher positive charge.

19. Fe2+ ferrous ion
Fe3+ ferric ion
FeCl2 ferrous chloride
FeCl3 ferric chloride
FeCl2 iron (II) chloride
FeCl3 iron (III) chloride

20. Chemical Nomenclature
Binary Ionic Compounds
BaCl2
barium chloride
K2O
potassium oxide
MgS
magnesium sulfide
Al2O3
aluminum oxide
2.7

21. Ionic Compounds Containing
Polyatomic Ions
1. Some polyatomics end in –ide:
OH-1 CN-1
2. Some polyatomics are cations:
NH4+1 Hg2+2

22. SO32-: sulfite
SO42-: sulfate
What do you do if there are more
than two forms of an anion
containing the same elements?

23. 3. Most polyatomic anions contain
multiple ions containing the same
two elements (O and another
element).
The anion with the smaller number of
oxygens uses the root of the element
plus –ite.
The anion with the higher number of
oxygens uses the root plus –ate.

24. ClO-1 hypochlorite
ClO2-1 chlorite
ClO3-1 chlorate
ClO4-1 perchlorate
The prefix hypo- is used in the
polyatomic with the fewest number
of oxygen atoms; the prefix per- is
used in the polyatomic with the
highest number of oxygen atoms.

25. Parenthesis are used when more than one polyatomic anion is in a
formula:
CaCO does not need parentheses
Cr2(SO4)3 There are 3 sulfate groups,
so parentheses are needed.

26. Iron (III) nitrate Fe(NO3)3 Calcium sulfate CaSO4
Examples of Polyatomic Ionic Compounds
Iron (III) nitrate Fe(NO3)3
Calcium sulfate CaSO4
Potassium dichromate K2Cr2O7
Chromium (II) permanganate Cr(MnO4)2
Sodium chlorate NaClO3
Sodium acetate NaC2H3O2
Tin (IV) phosphate Sn3(PO4)4

27. Binary Molecular Compounds
1. Usually composed of non-metallic
or metalloid elements.
2. Nonmetal/nonmetal compounds
don’t necessarily follow the
balance charge rules. Two or
more compounds may be formed
between two nonmetals.

28. 3. The element further left in the
periodic table is 1st in a molecule.
NO CO2
4. The element closest to the bottom
of a group is 1st in a molecule.
SO2 BrCl3

29. Example: N and O
N2O NO NO2 N2O4 N2O5
How do you differentiate between
different compounds composed of the
same elements?

30. To differentiate one compound from
another, use Greek numerical prefixes:
mono- hexa-
di- hepta-
tri- octa-
tetra- nona-
penta- deca-

31. 5. The prefix “mono-” is usually
omitted from the first element.
6. If the addition of a prefix causes
a/o or o/o to be next to each
other, the first vowel is usually
dropped.

32. Exceptions:
Compounds containing hydrogen:
Order can be first or second
May be named by systematic or
nonsystematic names (common names)
Name may or may not indicate
number of hydrogen atoms.

33. Molecular Compounds HI hydrogen iodide NF3 nitrogen trifluoride SO2
sulfur dioxide
N2Cl4
dinitrogen tetrachloride
TOXIC!
NO2
nitrogen dioxide
N2O
dinitrogen monoxide
Laughing Gas
2.7

34. Acids and Bases There are numerous definitions of
acids and bases; the definition given
here is that of an Arrhenius acid
and base:
Acid: yields H+ ions in water
Base: yields OH- ions in water

35. Acids without oxygen
1. When the acid is pure, the
hydrogen is named like a metal with
a +1 charge, and the ending –ide
is added to the anion.
HCl is hydrogen chloride
H2S is hydrogen sulfide

36. 2. When dissolved in water, refer
to compounds by their acid names:
drop the word hydrogen
add the prefix hydro to the anion
root
change the –ide ending to –ic,
followed by the word acid

37. 2.7

38. Oxyacids
1. Name the polyatomic anion, and
change –ite to –ous or change –ate
to –ic.
2. Add the word “acid.”

40. A base can be defined as a substance that yields
hydroxide ions (OH-) when dissolved in water.
NaOH
sodium hydroxide
KOH
potassium hydroxide
Ba(OH)2
barium hydroxide
2.7

41. barium chloride dihydrate
Hydrates are compounds that have a specific number of water molecules attached to them.
BaCl2•2H2O
barium chloride dihydrate
LiCl•H2O
lithium chloride monohydrate
MgSO4•7H2O
magnesium sulfate heptahydrate
Sr(NO3)2 •4H2O
strontium nitrate tetrahydrate
CuSO4•5H2O
CuSO4
2.7

42. 2.7

43. Organic chemistry is the branch of
chemistry that deals with carbon
compounds
The simplest organic compounds are
hydrocarbons, which contain only
hydrogen and carbon.

44. The simplest class of hydrocarbons are straight chains of C and H, and
are called alkanes.
CH4 methane
C2H6 ethane
C3H8 propane
C4H10 butane
C5H12 pentane
C6H14 hexane
C7H16 heptane
C8H18 octane
C9H20 nonane
C10H22 decane

45. Functional Groups Determine how an organic compound will react C H OH
NH2 C H OH O
methanol
methylamine
acetic acid
2.7