Transcript Section 8-2 - Columbia Community Unit School District 4

Section 8.2 Naming Molecules
• Translate molecular
formulas into binary
molecular compound
names.
oxyanion: a polyatomic
ion in which an element
(usually a nonmetal) is
bonded to one or more
oxygen atoms
• Name acidic solutions.
oxyacid
Specific rules are used when naming
binary molecular compounds, binary
acids, and oxyacids.
Why do atoms bond?
• Atoms gain stability when they share
electrons and form covalent bonds.
• Lower energy states make an atom more
stable.
• Gaining or losing electrons makes atoms
more stable by forming ions with noble-gas
electron configurations. (octet)
• Sharing valence electrons with other atoms
also results in noble-gas electron
configurations.
Why do atoms bond? (cont.)
• Atoms in non-ionic compounds share
electrons.
• Water is formed when Hydrogen and
Oxygen atoms share electrons.
• The chemical bond that results from sharing
electrons is a covalent bond.
• A molecule is formed when two or more
nonmetal atoms bond.
• Shared electrons are considered to be part
of the outer energy level of all the atoms
that share it.
• This type of bonding usually occurs
between elements near each other on the
periodic table.
• Most of this type of bonding is done with
nonmentals.
Molecular Nomenclature (Naming)
•
Prefix System (binary compounds)
1. Less electronegative atom
comes first.
2. The first element is always named first using the
entire element name.
3. Add prefixes to indicate the subscripts of each
atom. Omit the mono- prefix on first element.
4. Change the ending of the
second element to -ide.
Molecular Nomenclature
PREFIX
monoditritetrapentahexaheptaoctanonadeca-
NUMBER
1
2
3
4
5
6
7
8
9
10
• Name the following: P2O5
– Name the two elements:
• Phosphorus and Oxygen
• For the second element, the name is
changed to oxide.
• Add the prefixes to show the number
of atoms.
–Diphosphorus pentoxide
• Exception to the prefixes in table 8.3:
– The first element never uses the mono prefix
– If using a prefix would cause two consecutive
vowels, one of the them is often dropped to
avoid a difficult pronunciation.
• CO is monoxide NOT monooxide.
Molecular Nomenclature
• CCl4
– carbon tetrachloride
• N 2O
– dinitrogen monoxide
• SF6
– sulfur hexafluoride
Molecular Nomenclature
• arsenic trichloride
– AsCl3
• dinitrogen pentoxide
– N2O5
• tetraphosphorus decoxide
– P4O10
Molecular Nomenclature
• The Seven Diatomic Elements, exist
naturally as 2 atom molecules
H2 N2 O2 F2 Cl2 Br2 I2
H
N O F
Cl
Br
I
Naming Binary Molecular Compounds
(cont.)
• Many compounds were discovered and
given common names long before the
present naming system was developed.
(water H2O, ammonia NH3, hydrazine
N2H4, and nitric oxide NO are examples).
• These compounds are generally known by
their common names instead of their
scientific ones. What would their scientific
names be?
Naming Acids
• Acids
– Compounds that form [H+]in Solution (water).
– Formulas begin with ‘H’.
• Examples:
– HCl – hydrochloric acid
– HNO3 – nitric acid
– H2SO3 – sulfurous acid
Acid Nomenclature
• Anion Ending • Acid Name
• -ide
• -ate
• -ite
– Hydro-(stem)-ic acid
– (stem)-ic acid
– (stem)-ous acid
Acid Nomenclature
• HBr
– Br ends in -ide

hydrobromic acid

carbonic acid

sulfurous acid
• H2CO3
– CO3 ends in -ate
• H2SO3
– SO3 ends in -ite
Acid Nomenclature
• hydrofluoric acid
– Fluoride
 H + F-
 HF
• sulfuric acid
– Sulfate
 H+ SO42-  H2SO4
• nitrous acid
– Nitrite
 H+ NO2-
 HNO2
Naming Acids (cont.)
• The second word is always acid.
Notice that hydrogen is not part of the name.
Naming Acids (cont.)
• An acid, whether a binary acid or an
oxyacid, can have a common name in
addition to its compound name.
Section 8.2 Assessment
Give the name for the molecule HClO4.
A. perchloric acid
B. chloric acid
C. chlorous acid
D
C
A
0%
B
D. hydrochloric acid
A. A
B. B
C. C
0%
0%
0%
D. D