Hydrogen can
be +1 or
-1 (a hydride)
Charges on Group A Cations and Anions
+1
+2
+3 +2, +4 -3
-2 -1
Electrical neutrality- cations and anions combine in such a manner that the overall
charge on the compound is zero.
potassium (K+) and sulfide (S2-)
Aluminum (Al3+) and oxide (O2-)
combine as K2S (potassium sulfide)
combine as Al2O3 (aluminum oxide)
Ni +
Cu+
Mn4+
Hg+
Note that some metals form more than one kind of charged cation
examples: For Iron Fe 3+ or Fe 2+
For Lead Pb 2+ or Pb 4+
MUST MEMORIZE the metals which have variable charge
i.e., Cr, Mn, Fe, Ni, Cu, Hg, Pb, Sn, Tl
1
When NAMING these variable-charged cations, the charge must
be indicated by a Roman numeral in parenthesis.
Fe2+ is named Iron (II); Sn4+ is named Tin (IV);
Naming Binary Ionic compounds
CaO
CrF3
Iron (II) sulphide
NiCl
potassium nitride
La2Se3
sodium hydride
potassium bromide
tin (IV) iodide
HgS
Naming Compounds with Polyatomic Ions
Rules: 1) Identify the cation (may require a Roman numerial)
2) Identify the polyatomic anion . LEARN NAMES/ FORMULAS AND
CHARGES IN TABLE 2.3
2
Most names end in ite or ate
Several pairs of polyatomic ions are related by the presence or absence of
hydrogen atom
ex. CO32- (carbonate) HCO3- (hydrogen carbonate) PO43-,
H2PO4- (dihydrogen phoshate)
Oxoanion series - an atom of the same element is combined with different #
of O atoms
LEARN: 1) the common oxoanion ending in ate
2) adding one O: uses the prefix per
3) removing one O : changes the ate to ite
4) removing two O: uses the prefix hypo and change ate to ite
Ex: ClO- Hypochorite
ClO2- chlorite
ClO3- chlorate
ClO4- perchlorate
Naming Acids
Many acids are oxoacids
The names of oxoacids are based on the oxoanion name where ate ending
changes to ic
and ite changes to ous LEARN TABLE 2. 4
Other acids are hydrogen halides such as: HCl (g) = hydrogen chloride, HBr (g)
HI (g)
When HCl (g) dissolves on water its name changes to hydrochloric acid as is
written as HCl (aq)
3
Naming Polyatomic ion- containing compounds
and Acids
Barium nitrite
permanganate ion
Ca (OH)2
Hypochlorous acid
HNO2
Fe (III) sulphate
K2Cr2O7
sodium hydrogen
carbonate
Zn (CH3COO)2
hydrogen flouride
HI (aq)
(NH4)3 PO4
4
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