Download Section 2.8 - Foothill College

(Section 2.8)
Chemical Nomenclature: Names and Formula (Section 2.8)
Inorganic Compounds: The naming of ionic and molecular inorganic compounds should
be review for you! You are expected to be proficient in inorganic nomenclature
and to know some simple organic nomenclature. This is essential for success
in future topics covered in general chemistry!
Let’s start with Binary Ionic Compounds: Both Cation & Anion Monatomic
•
Cations are formed when an atom LOSES electrons
(oxidation).
lost e– (to anion)
•
Anions are formed when an atom GAINS electrons
(reduction).
gained e– (from cation)
For all ionic compounds,
the name and formula
lists the cation first and
the anion second. For
binary ionic compounds
the name of the cation is
the same as the name of
the metal. The anion is
named by adding the
suffix -ide to the root of
the nonmetal name.
Formulas of ionic
compounds are empirical
formulas, they reflect the
smallest whole number
ratio of cations to anions
that results in a net
charge of zero.
LiF is called lithium
fluoride.
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Using the Periodic Table to Determine Charges of Most
Main Group Monatomic Cations and Anions (Octet Rule)
•
•
–
–
–
–
–
Metals form cations:
They lose their valence
shell electrons.
– Group 1A :
lose how many e–?
– Group 2A:
lose how many e–?
– Metals of group 3A:
lose how many e–?
Nonmetals form anions:
They gain electrons to fill their
valence shell.
Group 4A nonmetal:
gain how many e–?
Group 5A nonmetals:
gain how many e–?
Group 6A nonmetals:
gain how many e–?
Group 7A:
gain how many e–?
H when bonded to a metal: gains
how many e–?
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What’s the formula of:
Aluminum Bromide
Calcium Phosphide
Name the following:
LiH
Ca2C
2
Some Common Monatomic Ions
What’s the formula of:
Chromium (II) Bromide
Cadmium sulfide
Name the following:
Pb3N2
Ag2O
Ni2+
Most main-group elements form one monatomic ion.
Most transition elements form two monatomic ions. When naming these, you MUST include
the charge in the name. We will do this using Roman Numerals: Fe2+ is called iron (II) in a
compound name.
Common transition elements that form only one ion-MEMORIZE these. In naming these, a
Roman Numeral is NOT used: Zn2+ is called zinc in a compound name.
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Systematic naming of a series
of oxoanions:
No. of O atoms
Prefix
per
hypo
Root
Suffix
root
ate
ClO4-
Example
perchlorate
root
ate
ClO3-
chlorate
root
ite
ClO2-
chlorite
root
ite
ClO-
hypochlorite
Models illustrating the covalent
bonding within phosphate and
hydrogen phosphate ions:
What’s the formula of:
Iron (II) Phosphate
Iron (II) Hydrogen Phosphate
Ammonium sulfate
Name the following: (Endings Matter!)
Cu(NO3)2
Cu(NO2)2
Cu3N2
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Hydrates
Hydrates are inorganic salts (ionic compounds) containing water molecules
combined in a definite ratio as an integral part of the crystal structure. Hydrates are
said to contain water of hydration. The specific number of water molecules in each
formula unit is indicated using Greek numerical prefixes:
Number
Prefix
Number
Prefix
Number
Prefix
1
mono-
4
tetra-
8
octa-
2
di-
5
penta-
9
nona-
3
tri-
6
hexa-
10
deca-
7
hepta-
Example:
Epsom Salts is magnesium
sulfate heptahydrate. The
formula is written as
MgSO4•7H2O or
MgSO4•(H2O)7
Heating a hydrate can remove the waters of hydration; the process can then be
reversed when water is present, such as in air with high humidity. A colorful example is
cobalt (II) Chloride which turns from blue to red upon hydration, and can therefore be used as a
water indicator.
Expose to moisture
Anhydrous
cobalt (II) chloride
What’s the formula?
Hydrated
cobalt (II) chloride hexahydrate
What’s the formula?
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Naming Binary Covalent Compounds
•
•
A binary covalent compound is typically formed by the combination of two non-metals.
Some of these compounds are very common and have trivial names, eg., H2O is
water and NH3 is ammonia.
For a binary covalent compound, the element with the lower electronegativity is generally
first in the name and formula. Its name remains unchanged.
•
•
The element that is second is named using the root with the suffix –ide.
Compounds are named using Greek numerical prefixes to indicate the number of atoms of
each element present with the following two exceptions: (1) prefixes are generally not used
for compounds with hydrogen listed as the first element in the formula (2) the first element in
the name has a prefix only when more than one atom of it is present (in other words, mono
is not used for the first element.)
•
When the element is oxygen and the prefix ends in a or o the, a or o of the
prefix is dropped for ease of pronunciation. For example, mono-oxide becomes
monoxide and tetra-oxide becomes tetroxide.
What’s the formula of:
dichlorine heptoxide
Hydrogen chloride Hydrogen chloride is a colorless gas (boiling point -85°C) that
consists molecules containing hydrogen and chlorine connected
by a polar covalent bond. Hydrogen chloride forms corrosive
hydrochloric acid on contact with water found in body tissues.
Inhalation of the fumes can cause coughing, chocking,
inflammations of the nose, throat, and upper respiratory tract.
0
3
1
acid
Name the following:
H 2S
CCl4
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Naming Acids
•
Litmus Paper
Red = Acid
In the Arrhenius definition, an acid is a substance that
+
produces hydrogen (H ) ions when dissolved in water. An
example is hydrochloric acid:
HCl(aq) –> H+(aq) + Cl–(aq)
HCl(g)
However, not all compounds that contain hydrogen behave
as acids (e.g. PH3 and CH4 are not acids). Acids generally
have hydrogen written first in their formula.
HCl(aq)
There are two types of acids important for Chemistry 1A:
1) Binary acid solutions form when certain gaseous compounds dissolve in water.
For example, when gaseous hydrogen chloride (HCl) dissolves in water, it forms a solution
called hydrochloric acid.
Prefix hydro- + anion nonmetal root + suffix -ic + the word acid
hydro + chlor + ic + acid
hydrochloric acid
2) Oxoacid names are similar to those of the oxoanions, except for two suffix changes:
-ate in the anion becomes –ic in the acid
-ite in the anion becomes –ous in the acid
The oxoanion prefixes hypo- and per- are retained.
Thus, BrO4– is perbromate, and HBrO4 is perbromic acid;
IO2– is iodite, and HIO2 is iodous acid.
What’s the formula of:
Hydrosulfuric acid
Sulfuric acid
Name the following:
H2CrO4(aq)
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Naming Some Simple Organic Compounds
•
Straight-Chain Alkanes:
Hydrocarbons are compounds that contain only carbon and hydrogen. Alkanes:
simplest type of hydrocarbon, all bonds are single
Alkanes are named using a root name followed by the suffix –ane.
methane
ethane
propane
•
In November 1776, methane was first scientifically
identified by Italian physicist Alessandro Volta in the
marshes of Lake Maggiore having been inspired to
search for the substance after reading a paper written
by Benjamin Franklin about "flammable air". Volta
captured the gas rising from the marsh, and by 1778
had isolated the pure gas. He also demonstrated
means to ignite the gas with an electric spark.
Alcohols: contain the –OH functional* group, covalently
bonded to a carbon atom (this is NOT a hydroxide).
Alcohols are named using a root name followed by the suffix –ol.
Vast amounts of methane
are locked up inside icelike frozen clathrates in
permafrost and the ocean
depths. When these
clathrates are brought to
the surface, methane gas
is released.
methanol (also called methyl alcohol)
methyl CH3–
ethanol (also called ethyl alcohol)
ethyl
CH3CH2–
*Functional Group: An atom or group of atoms that imparts characteristic
properties to an organic compound.
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Naming Some Simple Organic Compounds
•
Carboxylic acids: contain the –COOH functional group
Carboxylic acids are named using a root name followed by the suffix –oic acid.
methanoic acid
The common name, formic acid, is usually used.
ethanoic acid
What is the common name that is usually used?
•
When ethanol reacts with oxygen it forms
a weak acid called ethanoic acid. In an
open bottle of beer or wine, the reaction
happens naturally in the presence of
bacteria, and it is ethanoic acid that can
make beer or wine taste sour. Ethanoic
acid is found in vinegar ("vinegar" is old
french for “sour wine"). Vinegar is used
as a food flavoring and preservative.
Amines: contain the -NHx functional group where x can be 0, 1, or 2.
(chemically similar to NH3)
Amines are named using a root name followed by the suffix –amine. Greek numerical
prefixes are included as illustrated below.
methylamine
dimethylamine
trimethylamine
Amines are ubiquitous in biology. The
breakdown of amino acids releases
amines, famously in the case of decaying
fish which smell of trimethylamine.
Many neurotransmitters are amines, including
epinephrine, dopamine, serotonin and histamine.
ethylamine
Histamine
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