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 e- config. 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: SO3

2-

Oxyanions (cont.)

• Prefix:– Hypo-, anion w/ 1 less O than –ite– Per-, anion w/ 1 more O than -ate

• Ex: hypochlorite = ClO-,

chlorite = ClO2-

chlorate = ClO3-

perchlorate = ClO4-

Naming

• Name the cation– K+

• Name the anion– CO3

2-

• Name the salt– K2CO3 = potassium carbonate

Polyat. Ion Naming Practice

• NaOH– Sodium hydroxide

• LiClO2

– Lithium chlorite

• H2O2

– 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

– K O H = 0 K = +1• -2 +1

• Determine Cl in Ca(ClO3)2

• +2 -2

– Ca Cl2 O6 = 0 Cl = +10 = +5• +2 -12 2

Oxidation # Practice

• Determine N in NO3-

• -2

– N O3 - = -1 N = +5• -6

• Determine N in NH4+

• +1

– N H4 + = +1 N = -3• +4

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