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Ch 5 Ions and ionic cpds

Ch 5 Ions and ionic cpds. Chemical reactivity: Depends on electron configuration, noble gas least reactive (s&p filled) Octet rule: atoms tend to react to fill s&p valence electron shells. Chemical reactivity. Alkali metals and halogens most reactive elements

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Ch 5 Ions and ionic cpds

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  1. Ch 5Ions and ionic cpds Chemical reactivity: Depends on electron configuration, noble gas least reactive (s&p filled) Octet rule: atoms tend to react to fill s&p valence electron shells.

  2. Chemical reactivity • Alkali metals and halogens most reactive elements • Atoms lose, gain or share electrons to obtain an octet. • Alkali metals: ns1 configuration -> lose one electron (1+ change) • Halogens: ns2p5 configuration -> gain one electron (1- change) • Both reach an octet, filled s & p valence shell.

  3. Valence electrons • Use electron configuration to determine # of valence electrons . Look for highest PQ# s & p electrons. • Gain or lose electrons --> stable ion • Lose electrons --> cation (+) charge = # electrons lost • Gain electrons --> anion (-) charge = # electrons gained • Both cases reach an octet.

  4. Characteristics of stable ions • Filled s&p orbits of highest energy level • Noble gas configuration, octet • Ions have electric charge • Combine cation w/ anion in cpd • Conduct electric current in water • Transition metals ions w/out complete octet • Have multi oxidation states • All cations.

  5. Atoms and ions • Different chemical properties. • Metals --> cations, less energy to lose electrons (1 to 3) than to gain (5 to 7) • Nonmetals --> anions, less energy to gain electrons (1 to 3) than lose (5 to 7) • Cations and anions combine to form compounds with very specific properties separate from the metals and nonmetals properties.

  6. Ionic bonding and salts • Ionic bond: electrostatic attraction between opposite charges of cations and anions. • Forms solids called salts. • Salt: ionic cpd that forms when a metal atom or a positive radical replaces the hydrogen of an acid • Electrically neutral • Simple whole number ratio based on charge of ions • Distinctive crystal structure • Transferring electrons involve D energy. Overall energy D is exothermic. Na + E --> Na+ + e- Cl + e- --> Cl- + E

  7. Salt formation (pg 169 figure 9) • Endothermic (breaking bonds) • 1. Na(s) + E --> Na(g) sublimation • 2. Na(g) + E --> Na+ + e- ionization E • 3. Cl-Cl + E --> 2Cl(g) bond E • Exothermic (bond forming) • 4. Cl(g)+ e- --> Cl-(g) + E electron affinity • 5. Na+ (g) + Cl-(g) --> NaCl(s) + E lattice E

  8. Lattice energy • Energy associated with constructing a crystal lattice relative to the energy of all constituted atoms • Energy released w/ crystal structure of a salt as formed, key to salt formation. • Net energy is exothermic: • Energy to separate ions in water is supplied by water. • If a salt is not soluble, water does not have enough E to break ionic bonds

  9. Ionic cpds • Minerals of earth’s crust, cations + anion --> salt • Do not consist of molecules • ionic bonds are strong, attraction between opposite charges. • Distinctive properties (pg 171 table 1) • High boiling and melting pts • Solids at room temperature • Conduct electric current (l) or (aq) • Hard and brittle, ions arranged in repeating patterns, layers.--> shatter along cleavage plane.

  10. Salt crystals • Form repeating patterns --> crystal lattice • Repeating units, reason for crystal shape • Crystal structure depends on size & ratio on ions (pg 174 figure 12) • Salts have ordered packing arrangement • Until cell: smallest repeating unit in a crystal lattice. • Determined by x-ray diffraction crystallography. • Make model of arrangement of unit cells based on diffraction patterns.

  11. Names and formulas of ionic cpds • Naming ionic cpds: • Binary salts (2 elements, metal/nonmetal ions) • Cation: name metal, roman numeral if multi oxidation state. • Anion: root word of nonmetal and end in ide. • Writing ionic formulas: • Total positive charge = total negative charge. Net charge of cpd = 0 • 1. Write symbol & charge of cation & anion • Multiple oxidation state metals-> use roman numeral to indicate charge. (I) (II) (III) (IV) (V) (VI) • 2. Reduce if possible • 3. Cross over just the number --> subscripts.

  12. Practice • Write the formula for the following: • Copper (II) oxide, sodium fluoride, zinc chloride, aluminum sulfide, chromium (VI) oxide. • Name the following: • Ca3N2, FeI3, Na2O, AlCl3, SrO, MnO2

  13. Polyatomic ions • Ion made of two or more atoms covalently bonded with a net positive or negative charge (pg 178 table 2) • Form ionic bonds with opposite charged ions. • Naming polyatomic ions: • Oxypolyatomic ions • End in ite or ate as determined by # of oxygen's (SO3 2- sulfite, SO4 2- sulfate) • With addition of hydrogen atom (HPO4 2- monohydrogen phosphate) • Thio means replace oxygen with sulfur (S2O3 2- thiosulfate) • Naming or writing formula with polyatomic ion same as before. Use polyatomic name as is.

  14. Practice • Write the formula for the following: • Aluminum nitrate, magnesium phosphate, ammonium acetate, iron (II) thiosulfate, Copper (I) peroxide. • Name the following: • Ca(NO3)2, CuSO4, CuNO3, Na2CO3, K2Cr2O7

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