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] = 1s 2 2s 2 2p 6 3s 1 [Na + ] = 1s 2 2s 2 2p 6

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 + ] = 1s 2 2s 2 2p 6 = [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: Fe 2+ = Iron (II) Fe 3+ = 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 Al 2 S 3 –Aluminum sulfide Rb 2 O –Rubidium oxide FeF 2 –Iron (II) fluoride CrI 3 –Chromium (III) iodide Specify charge of transition metals

Writing Formulas Write the symbol & charges for the cation & anion –Aluminum oxide: Al 3+ O 2- Balance the charges by adding subscripts –Al 2 O 3

Formula Practice Calcium oxide –CaO Potassium nitride –K 3 N 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: NO 2 - = nitrite SO 4 2- = sulfate

Oxyanions Neg. polyatomic ion containing oxygen Suffix: –-ate, most common ion sulfate: SO 4 2- –-ite, anion w/ 1 less O sulfite: SO 3 2-

Oxyanions (cont.) Prefix: –Hypo-, anion w/ 1 less O than –ite –Per-, anion w/ 1 more O than -ate Ex: hypochlorite = ClO -, chlorite = ClO 2 - chlorate = ClO 3 - perchlorate = ClO 4 -

Naming Name the cation –K + Name the anion –CO 3 2- Name the salt –K 2 CO 3 = potassium carbonate

Polyat. Ion Naming Practice NaOH –Sodium hydroxide LiClO 2 –Lithium chlorite H 2 O 2 –Hydrogen peroxide CaCO 3 –Calcium carbonate

Writing Formulas Determine formula & charge of cation –Calcium = Ca 2+ Determine formula & charge of anion –Chlorite = ClO 2 - Balance charges (keep polyat. ion in parentheses if necessary) –Calcium chlorite = Ca(ClO 2 ) 2

Polyat. Ion Formula Practice Iron (II) hydroxide –Fe(OH) 2 Potassium dichromate –K 2 Cr 2 O 7 Aluminum phosphate –AlPO 4 Ammonium nitrate –NH 4 NO 3

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, O 2 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 (H 2 O 2 ) it’s –1 In cmpds, Gr. 1 & 2 & Al are +1, +2, & +3, respectively

Oxidation # Practice Determine K in KOH – K O H = 0K = Determine Cl in Ca(ClO 3 ) – Ca Cl 2 O 6 = 0Cl = +10 =

Oxidation # Practice Determine N in NO – N O 3 - = -1N = Determine N in NH –N H 4 + = +1N = -3 +4

Hydrate Ionic cmpd that contains water molecules in its crystal lattice –Naming: use prefixes (See Table 5-8) Na 2 CO 3 10H 2 O = 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 BaSO 4 5H 2 O –Barium sulfate pentahydrate MgSO 4 7H 2 O –Magnesium sulfate heptahydrate SrCl 2 2H 2 O –Strontium chloride dihydrate