CA Standards Students know atoms combine toform molecules by sharing electrons toform covalent or metallic bonds or byexchanging electrons to form ionicbonds. Students know salt crystals, suchas NaCl, are repeating patterns ofpositive and negative ions heldtogether by electrostatic attraction.
Bonds Forces that hold groups of atoms together and make them function as a unit. Ionic bonds – transfer of electrons Covalent bonds – sharing of electrons
The Octet Rule – Ionic CompoundsIonic compounds form so that each atom, bygaining or losing electrons, has an octet ofelectrons in its highest occupied energy level.Metals lose electrons to form positively-chargedcationsNonmetals gains electrons to form negatively-charged anions
Ionic Bonding:The Formation of Sodium Chloride Sodium has 1 valence electron Chlorine has 7 valence electrons An electron transferred gives each an octet Na: 1s22s22p63s1 Cl: 1s22s22p63s23p5
Ionic Bonding:The Formation of Sodium ChlorideThis transfer forms ions, eachwith an octet: Na+ 1s22s22p6 Cl- 1s22s22p63s23p6
Ionic Bonding:The Formation of Sodium ChlorideThe resulting ions come togetherdue to electrostatic attraction (opposites attract): Na+ Cl-The net charge on the compoundmust equal zero
Examples of Ionic compoundsMg2+Cl-2 Magnesium chloride: Magnesium loses two electrons and each chlorine gains one electronNa+2O2- Sodium oxide: Each sodium loses one electron and the oxygen gains two electronsAl3+2S2-3 Aluminum sulfide: Each aluminum loses two electrons (six total) and each sulfur gains two electrons (six total)
Metal Monatomic Ion name CationsLithium Li+ LithiumSodium Na+ SodiumPotassium K+ PotassiumMagnesium Mg2+ MagnesiumCalcium Ca2+ CalciumBarium Ba2+ BariumAluminum Al3+ Aluminum
Sodium Chloride Crystal LatticeIonic compounds formsolid crystals at ordinarytemperatures.Ionic compounds organizein a characteristiccrystal lattice ofalternating positive andnegative ions. All salts are ionic compounds and form crystals.
Properties of Ionic CompoundsStructure: Crystalline solidsMelting point: Generally highBoiling Point: Generally highElectrical Excellent conductors, Conductivity: molten and aqueousSolubility in Generally soluble water: