Ionic Compounds
Ch.5
(5-1) Ions
• Atom or group of atoms that has a
charge b/c it has lost or gained e• Ex: [Na] = 1s22s22p63s1
[Na+] = 1s22s22p6
Types of Ions
• Cation: + ion
– Lose e– Ex: K+
• Anion: - ion
– Gain e– Ex: Br-
Terms
• Electroneutrality: having = #’s of + & charges
• Isoelectronic: having the same econfig. as another atom
– [Na+] = 1s22s22p6 = [Ne]
Octet Rule
• Tendency of atoms to gain or lose e- so
that their outer s & p orbitals are full w/
8 e-
Transition Metal Ions
• Form cations
• Some have multiple ions due to d
orbitals
– Ex: Fe2+ = Iron (II)
Fe3+ = Iron (III)
Ionic Compounds
• Chemical cmpd composed of oppositely
charged ions
• Binary ionic cmpd: cation of 1 element &
anion of another
– Ex: ZnS, KBr
Naming Binary Ionic Cmpds
• Name of cation
– Ca = calcium
• Name of anion
– S = sulfur
• Drop anion suffix & add –ide
– CaS = calcium sulfide
Naming Practice
• Al2S3
– Aluminum sulfide
• Rb2O
– Rubidium oxide
• FeF2
– Iron (II) fluoride
• CrI3
– Chromium (III) iodide
Specify charge
of transition
metals
Writing Formulas
• Write the symbol & charges for the
cation & anion
– Aluminum oxide: Al3+O2-
• Balance the charges by adding
subscripts
– Al2O3
Formula Practice
• Calcium oxide
– CaO
• Potassium nitride
– K3N
• Tin (II) oxide
– SnO
• Copper (I) bromide
– CuBr
(5-2) Ionic Bond
• Force of attraction b/w ions of opposite
charge
Terms
• Coulombic force: attraction or repulsion
b/w 2 charged objects
• Halide: salt w/ halogen anion
– Ex: NaCl & KBr
Crystal Lattice
• Repetitive geometric arrangement of
atoms
• Unit cell: smallest repeating unit in a
crystal
NaCl
Lattice Energy
• E released when atoms, ions, or
molecules come together to form a
crystal
Properties of Binary Ionic
Cmpds
• Hard & brittle
– From crystal lattice
• Melt & boil at high temps.
– Need lots of E to break bonds
• Solids generally don’t conduct electricity
(5-3) Polyatomic Ion
• Group of bonded atoms that functions
as a single ion
• Ex: NO2- = nitrite
SO42- = sulfate
Oxyanions
• Neg. polyatomic ion containing oxygen
• Suffix:
– -ate, most common ion
• sulfate: SO42-
– -ite, anion w/ 1 less O
• sulfite: SO32-
Oxyanions (cont.)
• Prefix:
– Hypo-, anion w/ 1 less O than –ite
– Per-, anion w/ 1 more O than -ate
• Ex: hypochlorite = ClO-,
chlorite = ClO2chlorate = ClO3perchlorate = ClO4-
Naming
• Name the cation
– K+
• Name the anion
– CO32-
• Name the salt
– K2CO3 = potassium carbonate
Polyat. Ion Naming Practice
• NaOH
– Sodium hydroxide
• LiClO2
– Lithium chlorite
• H 2O 2
– Hydrogen peroxide
• CaCO3
– Calcium carbonate
Writing Formulas
• Determine formula & charge of cation
– Calcium = Ca2+
• Determine formula & charge of anion
– Chlorite = ClO2-
• Balance charges (keep polyat. ion in
parentheses if necessary)
– Calcium chlorite = Ca(ClO2)2
Polyat. Ion Formula Practice
• Iron (II) hydroxide
– Fe(OH)2
• Potassium dichromate
– K2Cr2O7
• Aluminum phosphate
– AlPO4
• Ammonium nitrate
– NH4NO3
Oxidation #’s
• # assigned to an atom in a polyatomic
ion or molecular cmpd based on an
assumption of complete transfer of e-
Assigning Oxid. #’s
• The sum of the oxid.#’s for all the atoms
in a cmpd = 0
• The sum of oxid.#’s for all atoms in a
polyatomic ion = charge on that ion
Assigning Oxid. #’s (cont.)
• Free (uncombined) elements = 0
– Na, O2
• Monatomic ion = charge of its ion
– K+ = +1
• More EN element in binary cmpd = its
charge if it were an ion
– NaCl: Cl = -1
Assigning Oxid. #’s (cont.)
• H = +1
– w/ a metal it’s –1
• F = -1
• O = -2
– w/ F it’s +2
– in peroxides (H2O2) it’s –1
• In cmpds, Gr. 1 & 2 & Al are +1, +2, &
+3, respectively
Oxidation # Practice
• Determine K in KOH
• -2 +1
– KOH =0
K = +1
• -2 +1
• Determine Cl in Ca(ClO3)2
• +2
–
-2
Ca Cl2 O6 = 0
• +2
-12
Cl = +10 = +5
2
Oxidation # Practice
• Determine N in NO3• -2
– N O3 - = -1
N = +5
• -6
• Determine N in NH4+
• +1
– N H4 + = +1
• +4
N = -3
Hydrate
• Ionic cmpd that contains water
molecules in its crystal lattice
– Naming: use prefixes (See Table 5-8)
• Na2CO3•10H2O = sodium carbonate
decahydrate
• Anhydrous: w/out water
Hydrate Prefixes
•
•
•
•
•
Mono - 1
Di - 2
Tri - 3
Tetra - 4
Penta - 5
•
•
•
•
•
Hexa - 6
Hepta - 7
Octa - 8
Nona - 9
Deca - 10
Naming Hydrates Practice
• BaSO4•5H2O
– Barium sulfate pentahydrate
• MgSO4•7H2O
– Magnesium sulfate heptahydrate
• SrCl2•2H2O
– Strontium chloride dihydrate