Forming Ionic Bonds Electron transfer: one atom loses electrons - another atom gains those electrons Positive and negative ions attract = ionic compound. Metal + oxygen = OXIDE Metal + nonmetals = SALT

Ionic Bonds Often binary (2 elements) e- lost = e- gained (always) Quick check: –How will sodium & chlorine combine? –How about calcium & sulfur? –How about lithium & phosphorus? –How about iron (III) & oxygen? Hint: use e- configurations or electron dot diagrams Then show box and table method to solve

Quick Check –How will sodium & chlorine combine? calcium & sulfur? lithium & phosphorus? iron (III) & oxygen?

Properties of Ionic Compounds Crystals (not molecules) = many cations and anions packed into a repeating pattern (crystal lattice). Chemical formula = ratio of atoms needed Fairly strong bond = large amount of energy to break. High melting & boiling points Often rigid & hard

More Properties If a liquid or solution, good conductors of electricity (electrolytes) If a solid, bad conductors because ions aren’t free to move EXOTHERMIC (almost always) – means the ionic compound is more stable & requires less energy, so heat is given off when forming Ex: hand warmers = iron + oxygen combining

Lattice Energy Energy to break apart 1 mole of ions Equals energy released when ions form More negative number = stronger bonds Smaller ions = greater lattice energy (nucleus is closer to the valence e-) Greater ionic charge = greater lattice NRG

Quick Check Which would have the greater lattice energy? –LiCl or LiBr –KF or RbF –NaCl or MgF 2 –SrCl 2 or MgO Which compound in each pair would have the higher melting point?