Beaker Breaker Draw the Lewis structure of the following:

1. Beaker BreakerDraw the Lewis structure of the following: • nitrate ion • sulfate ion • ammonium ion

2. Beaker Breaker • Is the following covalent or ionically bonded? • MgBr2 • NO3 • KI • F2O

3. 6-3 Ionic Bonding

4. Ionic Compound • composed of positive and negative ions that are combined so that the number of positive charges are equal to (cancel out) the number of negative charges • Na+1Cl-1 • Mg+2Cl2-1 (Mg+2Cl-1Cl-1) • Not called “molecules”…but called “formula units”

5. From a potential energy standpoint, why do ions form orderly arrangements known as crystal lattices?

6. Formation of Ionic Cmpds • Atoms form ions when they lose or gain e-s and attain a noble-gas configuration • Ions reach a lower potential E through the electrical forces of attraction between oppositely charged particles when they combine in an orderly arrangement known as a crystallattice. • Forces of repulsion (like-charged ions, adjacent e- clouds) balance the forces of attraction (opp-charged ions, nuclei-electron of adjacent ions)

7. Na: [Ne]3s1 • Cl: [Ne]3s23p5 • Na+1 sodium ionCl-1 chloride ion • [Ne] [Ar]

8. Sodium chloride, NaCl • The chemical formula of an ionic cmpd is the simplest formula of the cmpd…it does NOT represent a discrete GROUP of separate atoms like a molecule does • Covalent bonding: simplest unit is a molecule • Ionic bonding: simples unit is a formula unit

9. “Molecules” – discrete gps of atoms covalently bonded “Formula units” – simplest collection of atoms within an ionic cmpd i.e. NaCl..Na+1 doesn’t “belong” to any one neighbor

10. Lattice Energy • Term used to describe bond strength in ionic cmpds • Energy released when one mole of an ionic crystalline cmpd is formed from gaseous ions • Negative value indicates that E is released • The larger the value, the more E released, the more stable the bonding will be (true also for bond E) • i.e. NaCl –787.5 kJ/mol

11. Which ionic cmpd has a higher melting point….MgO or CaO ? • Lattice E must be overcome in order for an ionic cmpd to melt • Lattice E of MgO = -3760 kJ/mol • Lattice E of CaO = - 3383 kJ/mol • M. Pt of MgO = 2852 0C • M. Pt. of CaO = 275 0C

12. How do the forces that holds ions together compare to the forces that hold molecules together? • How do the forces BETWEEN ions compare to the forces BETWEEN molecules? • What effect will these differences have on properties like boiling/melting points, hardness, brittleness?

13. Covalent bonding • forms a “molecule” • Ionic bonding • within a crystal lattice

14. IONIC strong force that holds ions together (+, --) stronger forces of attraction between ions ∴higher melting & boiling pts; don’t vaporize at room temp MOLECULAR strong covalent bond within the atoms of each molecule weaker F of attraction between molecules ∴melt at low temps & many vaporize at room temp Ionic vs. Covalent Properties

15. Other ionic properties… • Hardness: tough for one layer to slide past another ∴ hard • Brittle: if ionic layers DO shift, they “snap”

16. How does conductivity in ionic cmpds compare to that in molecular cmpds?

17. IONIC non-conductors in solid state because ions can’t move conductors in molten state conductors when dissolved in H2O MOLECULAR non-conductors in all states Ionic vs. Covalent Properties

18. Polyatomic Ions • A charged group of covalently bonded atoms • Combine with ions of opposite charge to form ionic cmpds

19. Draw the Lewis structure for the phosphate ion • PO4-3 • P = 5 valence e-s = 5 e-s • 4 x O = 4 x 6 valence e-s = 24 e-s • -3 charge = 3 additional e-s + = 3 e-s 32 e-s