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)
note: replaces Table 2.12 in text
Ni +
Mn4+
Cu+
Co 3+
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 which metals have variable charge
i.e., Cr, Mn, Fe, Co, 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 numeral)
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 phosphate)
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
Acids and Bases
Acid- A substance that provides H+ ions in water
examples : HCl, H2SO4
Base- A substance that provides OH- ions in water
examples: NaOH, Ba(OH)2
Naming Bases
Similar to naming compounds with polyatomic ions.
In this case, the polyatomic ion is the hydroxide ion (OH-)
KOH
Ba (OH)2
potassium hydroxide
barium hydroxide
3
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 and is
written as HCl (aq)
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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