Transcript Naming Compounds

Naming Compounds
Writing Formulas
and Equations
Larry Scheffler
Lincoln High School
Naming Compounds
The chemical formula represents the composition of
each molecule.
In writing the chemical formula, in almost all cases the
element farthest to the left of the periodic table is written
first.
So for example, the chemical formula of a compound
that contains one sulfur atom and six fluorine atoms is
SF6.
If the two elements are in the same group, the symbol of
the element of that is lower in the group (i.e. heavier) is
written first e.g. IF3.
Naming Ionic Compounds
Ionic compounds are combinations of positive
and negative ions.
In writing the chemical formula, the positive ion
is written first, It is then followed by the name of
the negative ion.
Monatomic anions end in ide. Special endings
apply for polyatomic ions
Examples
NaCl Sodium chloride
BaF2 Barium Fluoride
ZnO Zinc Oxide
Names of Polyatomic Ions
with Oxygen
Polyatomic ions
usually contain
oxygen in addition
to another element.
Normally, they have
a negative charge.
They end in either
"ate" or "ite"
depending on the
number of oxygen
atoms present.
ClOClO2ClO3-
hypochlorite
chlorite
chlorate
ClO4-
perchlorate
NO2-
Nitrite
NO3PO33-
Nitrate
phosphite
PO43-
phosphate
SO32SO42-
sulfite
sulfate
Polyatomic Ion -- Exceptions
Most polyatomic ions contain oxygen
– Their names end in “ite” or “ate”.
There are several exceptions:
OHCNSCN-
hydroxide
cyanide
thiocyanate
Elements with Multiple Cations
1.
2.
3.
4.
When an element can form more than one cation, a
Roman numeral is used to distinguish the oxidation
state of the compound.
Iron, Tin, Lead, Copper, and are common elements with
more than one cation.
Examples
PbSO4 = lead (II) sulfate
This compound is formed
from Pb2+ and SO42Pb(SO4)2 = lead (IV) sulfate This compound is formed
from Pb4+ and SO42Fe(OH)2 = iron (II) hydroxide This compound is
formed from Fe2+ and OHFe(OH)3 = iron (III) hydroxide This compound is
formed from Fe3+ and OH-
Examples of Ionic Compounds
1.
2.
3.
4.
5.
6.
7.
8.
9.
NaCl
ZnF2
KOH
Ca(NO3)2
BaSO3
Al2(SO4) 3
Ca3(PO3)2
NH4Cl
(NH4)2CO3
=
=
=
=
=
=
=
=
=
Sodium chloride
Zinc fluoride
Potassium hydroxide
Calcium nitrate
Barium Sulfite
Aluminum sulfate
Calcium phosphite
Ammonium chloride
Ammonium carbonate
Naming Covalent Compounds
When naming covalent compounds, the name of the
first element in the formula is unchanged.
The suffix “-ide” is added to the second element.
Often a prefix to the name of the second element
indicates the number of the element in the
compound
Covalent molecules use prefixes; Ionic molecules use
Roman Numerals (most of the time).
Examples:
SF6 – sulfur hexafluoride
P4O10 – tetraphosphorous decoxide
CO – carbon monoxide
CO2 – carbon dioxide
Naming Covalent Compounds
Greek Prefixes:
MonoDiTriTetraPentaHexaHeptaOctaNonaDeca-
Covalent molecules with
multiple possibilities
Example of exceptions:
(not normally done, but you may come across)
–
A Roman Numeral is used to indicate the state of the more
positive element
N2O = Nitrogen (I) oxide Since oxygen has a 2charge, the nitrogen must be 1+ to balance the
charges. Also known as dinitrogen monoxide
2. N2O3 = Nitrogen (III) oxide Since oxygen has a 2charge, the nitrogen must be 3+ to balance the
charges. Also known as dinitrogen trioxide
1.
Binary compounds of Hydrogen
The binary compounds of hydrogen are special
cases. They were discovered before a convention
was adopted and hence their original names have
stayed.
Water H2O is not called dihydrogen monoxide
Hydrogen forms binary compounds with almost all nonmetals except the noble gases.
Examples
HF - hydrogen fluoride
HCl - hydrogen chloride
H2S - hydrogen sulfide
Acids
•
When many hydrogen compounds are dissolve in water
they take on the form of an acid. Special rules apply to
acids.
• The “ide” suffix becomes “hydro” “-ic”,
• The “ite” suffix becomes “ous”
• The “ate” suffix becomes “ic”
Cl-
Chloride
HCl
Hydrochloric Acid
NO2-
Nitrite
HNO2
Nitrous Acid
NO3-
Nitrate
HNO3
Nitric Acid
SO32-
Sulfite
H2SO3
Sulfurous Acid
SO42-
Sulfate
H2SO4
Sulfuric Acid
PO33-
Phosphite
H3PO3
Phosphorous Acid
PO43-
Phosphate
H3PO4
Phosphoric Acid
CO32-
Carbonate
H2CO3
Carbonic Acid
Writing Formulas for Ionic
Compounds
Write the positive ion (cation) first, then the
negative ion.
The positive charges must balance the negative
charges.
Use subscripts to show how many times each
ion must appear in order for the charges to
balance. A subscript is not used if the ion
appears only once. (Crisscross Method)
Use parenthesis around polyatomic ions that
appear more than once in the formula
Examples
1.
2.
3.
4.
5.
6.
7.
8.
9.
Na+
Zn2+
K+
Ca2+
Fe2+
Fe3+
Ca2 +
NH4+
NH4+
and Cland Brand OHand OHand SO42and SO42and PO43and Cland CO32-
= NaCl
= ZnBr2
= KOH
= Ca(OH)2
= FeSO4
= Fe2(SO4) 3
= Ca3(PO4)2
= NH4Cl
= (NH4)2CO3
Diatomic Molecules
Certain elements
exist as diatomic
molecules in nature
The “Seven at 7”
– Starting at #7, in the
shape of a 7 (sort of),
there are 7 elements
H2
Hydrogen
N2
Nitrogen
F2
Fluorine
O2
Oxygen
I2
Iodine
Cl2 Chlorine
Br2 Bromine
Diatomic Molecules
Certain elements
exist as diatomic
molecules in nature
The “Seven at 7”
– Starting at #7, in the
shape of a 7 (sort of),
there are 7 elements
H2
Hydrogen Have
N2
Nitrogen
No
F2
Fluorine
Fear
O2
Oxygen
Of
I2
Iodine
Ice
Cl2
Chlorine
Cold
Br2
Bromine
Bunnies