Ionic bonds and ionic compounds<br />Chapter 6.3<br />
Objectives<br />Compare and contrast a chemical formula for a molecular compound with one for an ionic compound<br />Discuss the arrangements of ions in crystals<br />Define lattice energy and explain its significance<br />List and compare the distinctive properties of ionic and molecular compounds<br />Write the Lewis structure for a polyatomic ion given the identity of the atoms combined and other appropriate information<br />
Ionic Compounds<br />Defined as : compound composed of positive and negative ions that are combined so that the numbers of positive and negative charges are equal.<br />Sodium Chloride<br /><ul><li>Most ionic compounds exist as
3-D network of positive and negative ions mutually attracted to one another.
Chemical formula is simply written as NaCl.</li></li></ul><li>Formula Unit<br />Defined as : the simplest collection of atoms from which an ionic compound’s formula can be established.<br />Calcium Fluoride<br />Potassium chloride<br />Cl<br />1 to 1 ratio<br />1 to 2 ratio<br />K<br />Ratio depends on charges of ions!<br />KCl<br />CaF2<br />
Formation of Ionic compounds<br />Using electron dot notation to show ionic bonding<br /> Na Cl<br />Sodium atom Chlorine atom<br />Na + Cl Na+1 + Cl -1<br />Sodium atom Chlorine atom Sodium cation Chlorine anion<br />Ca + F + F Ca+2 + F -1 + F -1<br />Sodium atom Fluorine atom Fluorine atom Calcium cation Fluorine anion Fluorine anion<br />
Characteristics of Ionic Bonding<br />Ionic crystal has minimum potential energy<br />Crystal Latticeis formed<br />Orderly arrangement of ions <br /><ul><li>Lattice energy
Energy released when one mole of an ionic crystalline compound is formed from gaseous ions.
Energy is released when crystals are formed</li></li></ul><li>Compare ionic and molecular compounds<br />Ionic compound<br />Very strong attractive forces<br />High melting and boiling points<br />Hard and brittle<br />Not electrical conductors (in solid state)<br />Are electrical conductors (in molten state and when dissolved)<br />Molecular compound<br />Attractive force between molecules aren’t as strong<br />Low melting and boiling points, many are gases at room temperature<br />Notelectrical conductors<br />