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Chapter 5

Molecules and
Compounds
(Naming)

Molecules and Compounds
(Naming)

Molecules and Compounds
(Naming)
Review from previous lecture
What is an ionic compound composed of?
What is a covalent compound composed of?

IUPAC
• The International Union of Pure and Applied
Chemistry, IUPAC, has set rules for naming
compounds
...

• These rules are still in use today
...
We will only naming inorganic
coumpounds
...

• There are 5 common classes of inorganic
compounds:
1) binary ionic

4) binary acid

2) ternary ionic

5) ternary oxyacid

3) binary molecular

Classification of Compounds
• Below is a flow chart for the classification of
inorganic compounds
...

– KCl and AlCl3 are binary ionic compounds
...

– KNO3 and Al(NO3)3 are ternary ionic
compounds
...

– Some examples of binary molecular compounds
are ammonia, NH3, methane, CH4, and carbon
dioxide, CO2
...

• A binary acid is an aqueous solution of a
compound containing hydrogen and one other
nonmetal
...

• A ternary oxyacid is an aqueous solution of a
compound containing hydrogen, oxygen, and one
other nonmetal
...


Ex
...
Zn3(PO4)2
2
...
Co2O3
4
...
HBr(aq)

Helpful Tip
Before you go any further in the class notes, stop and make sure
you can classify all compounds as either
...
Binary Ionic: (2 els
...
NaCl)
2
...
, at least one metal and nonmetal, Ex
...
Binary Molecular: (2 els
...
NO)
4
...
HCl (aq))
5
...
HNO3 (aq)
*** It is impossible to name compounds if you don’t put them in the proper
category first!!!

Classification of Ions
• Below is a flow chart for the classification of ions
...

• Cations are named for the parent atom followed by
the word “ion”
...

Fe2+ is the iron(II) ion
Fe3+ is the iron(III) ion

• This is called the Stock system of naming cations
...


Remember: 5 Exceptions!!!

Monoatomic Cations
• Name the following monoatomic cations:
1
...
Sr2+
3
...
Zn2+
5
...
Mg2+

Monoatomic Anions
• Nonmetals can gain valence electrons and become
negatively charged anions
...

Nonmetal

Symbol for Ion

Base name

Anion name

fluorine

F–

Fluor-

fluoride

chlorine

Cl–

Chlor-

chloride

bromine

Br–

Brom-

bromide

iodine

I–

Iod-

iodide

oxygen

O2–

Ox-

oxide

sulfur

S2–

Sulf-

sulfide

nitrogen

N3–

Nitr-

nitride

phosphorus

P3–

Phosph-

phosphide

Polyatomic Anions
• Polyatomic anions generally contain one or more
elements combined with oxygen
...

• Most oxyanions have names that end in the suffix ate
...

– NO2- is the nitrite ion
– SO32- is the sulfite ion

• Notice that these oxyanions have one less oxygen
than sulfate (SO42-) and nitrate (NO3-)
...


More Polyatomic Anions
• The formula for the chlorate ion is ClO3-
...
Chlorite must
have one less oxygen then chlorate, so its formula is
ClO2-
...

• There are three polyatomic ions that end in -ide:
– hydroxide, OH-, cyanide, CN-, and peroxide, O22-

Memorize these
3 exceptions

Some Common Polyatomic Ions

You will be
given this
handout on a
test!

Writing Ionic Formulas
• An ionic compound is composed of positive and
negative ions
...

• A formula unit is always neutral, so the total
positive charges must always equal the total
negative charges inside a formula unit
...


Formulas of Ionic Compounds
• If the ions in the ionic compound have the same
charge, the formula unit contains one of each ion
...

Mg2+ and S2- combine to form MgS
...

Ca2+ and Cl- combine to form CaCl2
...


Crossover Rule
• You can quickly verify that the chemical formula
is written correctly by crossing over the charge on
each ion
...


+1

Both

+2

NEED TO
MEMORIZE!

+3 +/- -3 -2 -1

No
Ions

Then…
...
Li+ and Cl-

2
...

Mg2+ and SO42- combine to form MgSO4
K+ and ClO3- combine to form KClO3

• If the charges are not equal, the total charge must
equal zero
...

Al3+ and CO32- combine to form Al2(CO3)3

Writing Formulas of Ternary Ionic
Compounds
Write the formula of the following ternary
compounds given their constituent ions:
1
...
Co2+ and OH-

Determining Ionic Charge
• If an ionic compound contains a metal which can
have more than one ionic charge, we must
determine the charge on the ion
...

• What is the charge on the iron ion in Fe2O3?

How To Name Compounds
To name compounds correctly, you must :
1
...

binary ionic, ternary ionic, etc)
(Already covered at beginning of chapter)

2
...
)

Classification of Compounds

Naming Binary Ionic Compounds
• When naming ionic compounds, we combine the
cation and anion name (drop the word “ion”) with
the cation first and the anion second
...

• What is the name of cinnabar, HgS?
•

Hg2+ is the mercury(II) ion and S2- is the sulfide ion, so the
name is
mercury(II) sulfide
...
LiBr
2
...

• What is the formula of iron(III) fluoride?
Iron(III) has a +3 charge, Fe3+; and fluoride has a
1 charge, F-
...


Determining Formulas for

Binary Ionic Compounds
Provide the formula for the following Binary Ionic
Compounds:
1
...
Iron (III) nitride

Classification of Compounds

Naming Ternary Ionic Compounds
• We name ternary ionic compounds like binary ionic
compounds: the cation name followed by the anion name
...


• If we have a metal that can have more than one oxidation
state (charge), we have to use roman numerals indicating
its charge
...

The name is cobalt(III) chlorate

Naming Ternary Ionic Compounds
Supply a systematic name for each of the following
ternary ionic compounds:
1
...
Co(ClO2)3

Naming Ternary Ionic Compounds
Supply a systematic name for each of the following
ternary ionic compounds:
3
...
Hg(NO2)2

Naming Ternary Ionic Compounds
Provide the formula for each of the following ternary
ionic compounds:
1
...
copper(II) chlorite

Classification of Compounds

Binary Molecular Compounds
• Binary molecular compounds are composed of two
nonmetal elements
...

• IUPAC has set the following order for writing the
elements in a binary molecular compound:
– C, P, N, H, S, I, Br, Cl, O, F

• Notice they are arranged according to increasing
electronegativity
...

• The number of atoms of each element must be
indicated by Greek prefixes
...
What is the name of P4S3?
– There are 4 P atoms, use tetra– There are 3 S atoms, use tri– The name for P4S3 is tetraphosphorous trisulfide
...

• If there is only one atom of the first element, the
mono- is never used:
– IF6 is iodine hexafluoride (not monoiodine hexafluoride)

Naming Binary Molecular Compounds
Examples:
CO2

P4O10

NO2

N2O5

SO3

BF3

S2O7

CCl4

Note: When the vowels from the prefix and suffix interfere (i
...
, there are two in a
row), you usually drop the vowel from the prefix
...

• The formula of an acid always begins with H:
– HF (aq)

• Binary acids are named by using the prefix hydrobefore the element stem and adding the suffix
-ic acid
...

ex) HCl (aq) = Hydrochloric acid

• Binary molecular compounds = two non-metals
(might also have hydrogen) but is not
dissolved in water
...

• If the acid is derived from an oxyanion ending in ate, the suffix is changed to -ic acid
...

– HNO2 (aq) is nitrous acid (from NO2-, nitrite ion)

Ternary Oxyacids

Remember: Never use “hydro–” prefix for ternary oxyacids
...
Li3PO4 = ternary ionic— lithium phosphate
2
...
H3PO4 (aq)= ternary oxyacid— phosphoric acid
4
...
H3N (aq)=binary acid— hydronitrate
6
...
(Already covered this way)
2) Latin System:
• We add the following endings to their old (Latin) root
names:
• “ous” ending for ion with the LOWER charge
• “ic” ending for ion with the HIGHER charge

Naming Ionic Compounds - Latin
Metal
Chromium

Iron
Cobalt

Copper

Tin
Lead

Symbol for Ion

Name

Older name

Cr2+

Chromium(II)

Chromous

Cr3+

Chromium(III)

Chromic

Fe2+

Iron(II)

Ferrous

Fe3+

Iron(III)

Ferric

Co2+

Cobalt(II)

Cobaltous

Co3+

Cobalt(III)

Cobaltic

Cu+

Copper(I)

Cuprous

Cu2+

Copper(II)

Cupric

Sn2+

Tin(II)

Stannous

Sn4+

Tin(IV)

Stannic

Pb2+

Lead(II)

Plumbous

Pb4+

Lead(IV)

Plumbic

Naming Ionic Compounds - Latin
Name the following compounds using the
Naming system:
1
...
PbO= plumbous oxide/ lead 2 oxide
3
...
Sn(CO3)2=stannic carbonate/tin 2 carbonate

Latin

Conclusions
• Most inorganic compounds do not contain carbon
...

• Ternary ionic compounds are composed of a metal,
a nonmetal, and oxygen
...

• Acids are composed of hydrogen and a nonmetal
atom or an oxyanion
...

• Cations with more than one possible charge have
their charge indicated with Roman numerals in
parentheses
...
Then anion has the suffix -ide added
...


Conclusions Continued
• The simplest representative unit for a molecular
compound is a molecule
...

• The name of the first element is the same, the
suffix -ide is added to the second element
...


Conclusions Continued
• An acid is an aqueous solution of a compound
containing hydrogen and a nonmetal or an
oxyanion
...

• Ternary oxyacids are named by changing the -ate
suffix on the oxyanion to -ic acid or the -ite suffix
on the oxyanion to -ous acid
...
5 – 5
...




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