Presentation on theme: " 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."— Presentation transcript:
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:
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)
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!
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