2.  example: the formation of sodium chloride (NaCl)  Na gives up its only valence e- to form a stable Na + cation  1s 2 2s 2 2p 6 3s 1  1s 2 2s 2 2p 6 [Na] [Na + ] + e-

3.  Cl, with only 7 valence e-, acquires that e- to form a stable Cl - anion  e- + 1s 2 2s 2 2p 6 3s 2 3p 5  1s 2 2s 2 2p 6 3s 2 3p 6 e- + [Cl] [Cl - ]

4.  the force of attraction between the 1+ charge on the sodium cation and the 1- charge on the chloride anion creates the ionic bond in sodium chloride (NaCl)  http://visionlearning.com/library/flash_viewer.php?oid=1349&mid=55 http://visionlearning.com/library/flash_viewer.php?oid=1349&mid=55

5.  salt –(def) an ionic compound that forms when a metal atom replaces the hydrogen in an acid  other common salts are potassium chloride (KCl) and calcium iodide (CaI 2 )  salts are electrically neutral ionic compounds  salts are made up of cations and anions held together by ionic bonds  the ratio of cations to anions is always a simple whole number ratio  example: NaCl is made of sodium cations and chloride anions bonded in a 1:1 ratio  example: CaI 2 is made of calcium cations and iodide anions bonded in a 1:2 ratio

6.  the attraction between cations and anions in ionic compounds creates crystal structures  ionic compounds are not made up of molecules  even though the cation to anion ratio in NaCl is 1:1, there is no single cation to anion “bond”  each sodium cation [Na + ] is surrounded by [Cl - ] anions  each [Cl - ] anion is surrounded by [Na + ] cations  this causes the ions to be pulled into a tightly packed structure called a crystal lattice

7.  ionic compounds have no overall charge  the ratio of cations (+) to anions (-) are balanced so that the compound has no overall charge  example: magnesium oxide (MgO)  each magnesium cation (Mg 2+ ) is balanced by an oxygen anion (O 2- )

8.  both attractive and repulsive forces exist within an ionic compound  the repulsive charges arise from like-charged ions  cations repel other cations  anions repel other anions  attractive forces arise from oppositely-charged ions  anions attract cations; cations attract anions  attraction extends beyond the single cation/anion pair

9.  each [Na + ] cation is surrounded by 6 [Cl - ] anions  each [Cl - ] anion is surrounded by 6 [Na + ] cations  this resulting crystal structure significantly increases the attractive force between ions  overall the attractive forces are much stronger than the repulsive forces making ionic bonds very strong http://www.avogadro.co.uk/structure/chemstruc/ionic/g-ionic.htm

10.  the attraction between ions in ionic compounds is not limited to isolated cation/anion pairs  ionic compounds are created from repeating patterns of ions held together by attractive forces (a) atomic-level view of the crystal lattice structure of NaCl (b) sodium chloride crystals highly magnified

11.  these repeating patterns of bonded ions create a crystal lattice  crystal lattice –(def) the regular pattern in which a crystal is arranged  the crystal lattice is made of repeating units called a unit cell  unit cell –(def) the smallest portion of a crystal lattice that shows the 3-dimensional pattern of the entire lattice  example: NaCl unit cell http://www.avogadro.co.uk/structure/chemstruc/ionic/g-ionic.htm

12.  since different salts have different cation to anion ratios, different salts have different crystal structures (see figure 12 p. 174)

13.  this is due to the strong attraction between the ions  a considerable amount of energy (heat) has to be applied to allow the ions to change state from solid to liquid (melting) and liquid to gas (boiling)  as a result, ionic compounds are rarely gases at room temperature

14.  hard---meaning they can resist a large applied force  brittle---meaning a force it can’t resist will cause the crystal to fracture along widespread shatter-lines

15.  2 conditions must exist for a substance to conduct electricity: 1) the substance must contain charged particles 2) the particles must be free to move (a) Pure water does not conduct a current, so the circuit is not complete, so the light does not light. (b) Water containing a dissolved salt conducts electricity and the bulb lights.

16.  ionic solids are not good conductors because the ions are not free to move (see fig 11 p. 172)  both molten salts and dissolved salts can conduct electricity because the ions are free to move (see fig 11 p. 172)