 e-’s responsible for chem props of atoms  in outer energy level  s and p e-’s in outer energy level  Core e-’s – energy levels below.

1) same outer e- configuration 2) same valence e-’s  valence e-’s easily determined  equal to group # for representative element  2A: Be, Mg, Ca, etc. have 2 valence e-’s

 valence e-’s  symbol represents nucleus & core e-’s  Each side = orbital (s or p)  dot = valence e- (8 max)  don’t pair up until they have to (Hund’s rule) X (s) (p x ) (p z ) (p y )

Electron Dot diagram for Nitrogen l Nitrogen has 5 valence e- l write symbol N l put first 2 e- on rt side l Add remaining e-’s CCW

The Octet Rule l Noble gases unreactive (Ch 6) l Octet Rule: noble gas configuration l 8 outer level (stable) l noble gas has 8 e-’s in outer level l (He has 2)

 Metals lose e-’s to attain a noble gas configuration (NGC).  They make + ions (cations)  Na 1s 2 2s 2 2p 6 3s 1 1 valence e-  Na 1+ 1s 2 2s 2 2p 6 (NGC w/ 8 valence e-’s)

 Metals have few valence e-’s (usually 3 or less); calcium has only 2 valence e-’s Ca

 Metals few valence e-’s  Metals lose Ca

 Form + ions Ca 2+ NO DOTS shown for cation “calcium ion”. This is named the “calcium ion”.

 Scandium (21)  e- configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 1  lose 2e - (2+), or lose 3e - (3+) Sc = Sc 2+ Scandium (II) ion Scandium (III) ion Sc = Sc 3+ Sc

 Silver (47)  Predicted configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9  Actual configuration is: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 1 4d 10 Ag = Ag 1+ (can’t lose any more, charges of 3+ or greater are uncommon)

 Silver did the best job it could, but it did not achieve true NGC  “pseudo-noble gas configuration”

 Nonmetals gain e-’s to attain NGC  - ions (anions)  S = 1s 2 2s 2 2p 6 3s 2 3p 4 = 6 valence e-  S 2- = 1s 2 2s 2 2p 6 3s 2 3p 6 = NGC  Halide ions - ions from halogens that gain e-’s

 Nonmetals have many valence e-’s (usually 5+)  gain e-’s P 3- (called “phosphide ion”, and should show dots)

 All atoms react to achieve NGC  Noble gases… s 2 p 6  8 valence e-’s (stable)  octet rule Ar Electron dot activity

Practice problems p. 193  1. Write the name and symbol of the ion formed when  A. A sulfur atom gains two electrons  B. An aluminum atom loses three electrons

Practice problems p. 193  2. how many electrons are lost or gained in forming each ion?  A. Ba 2+ B. As 3- C. Cu 2+

 OBJECTIVES:  Explain the electrical charge of an ionic compound.

 OBJECTIVES:  Describe three properties of ionic compounds.

 Anions & cations – (+ and -)  electrostatic forces  Formula unit - simplest ratio of elements in ionic cmpd  bond thru transfer (lose/gain) of e-’s  e-’s transferred to achieve NGC

Na Cl metal (sodium) loses one valence e- Cl needs 1 e- for octet

Na + Cl - NOTE: NO DOTS shown for cation Ionic Bonding 0:38 dot & cross diagrams 2:57

 All e-’s must be accounted for,  each atom has NGC (stable) CaP combining calcium and phosphorus:

CaP

Ca 2+ P

Ionic Bonding Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca

Ionic Bonding Ca 2+ P 3- Ca P

Ionic Bonding Ca 2+ P 3- Ca 2+ P

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

Ionic Bonding = Ca 3 P 2 Formula Unit chemical formula - shows kinds and numbers of atoms in smallest representative particle of substance. Formula Unit - smallest representative particle in ionic cmpd Ionic bonds 6:28

1. Crystalline solids - regular repeating arrangement of ions in the solid: Fig. 7.9, page 197  Ions strongly bonded  Rigid structure 2. High melting points  Coordination number- # of ions of opposite charge surrounding it Chemistry of salt 6:23

- Page 198 Coordination Numbers: Both the sodium and chlorine have 6 Maximizes contact btwn opp charges Both the cesium and chlorine have 8 Each titanium has 6, and each oxygen has 3 NaCl CsCl TiO 2

3. Melted ionic cmpds conduct  Crystal structure breaks down  ions free to move (molten or aqueous)

 OBJECTIVES:  Model the valence electrons of metal atoms.

 OBJECTIVES:  Describe the arrangement of atoms in a metal.

 OBJECTIVES:  Explain the importance of alloys.

 How metal atoms are held together in the solid.  Metals hold on to their valence e-’s weakly.  positive ions (cations) floating in sea of e-’s (Fig. 7.12, p.201)

 e-’s free to move thru solid.  Metals conduct electricity

 Hammered / shaped  ductile - drawn into wires.  malleability & ductility explained in terms of mobility of valence e-’s

- Page 201 1) Ductility2) Malleability Due to the mobility of the valence electrons, metals have: and Notice that the ionic crystal breaks due to ion repulsion!

Force

 Mobile e-’s allow atoms to slide by  like ball bearings in oil Force

 Strong Repulsion breaks crystal apart, b/c similar ions next to each other Force

 Metals are crystalline  Metals w/ 1 type of atom simplest crystalline solid  Compact & orderly patterns Fig p.202: 1. Body-centered cubic: Fig p.202:  every atom has 8 neighbors (except atoms on surface)  Na, K, Fe, Cr, W

2. Face-centered cubic:  every atom has 12 neighbors  Cu, Ag, Au, Al, Pb

3. Hexagonal close-packed  12 neighbors  different pattern due to hexagonal  Mg, Zn, Cd

 We use metals every day, few pure metals  Alloys made by melting a mixture of ingredients, then cooling  Brass: alloy of Cu and Zn  Bronze: Cu and Sn

 Properties superior to pure element  Sterling Ag (92.5% Ag, 7.5% Cu)  harder than pure Ag  Soft enough for jewelry & tableware  Steels important  corrosion resistant, ductility, hardness, toughness, cost efficient

 Table 7.3, p.203 – lists alloys  Types:  a) substitutional alloy- atoms in components are about same size  b) interstitial alloy- atomic sizes differ;  smaller atoms fit in spaces btwn larger  “Amalgam”- dental fillings, contains 50%Hg, 22%Ag, 14%Sn, 8%Cu

Alchemy  Turning cheap metals into “gold”