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- configuration2) 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)
(px)
(pz)
(py)
Electron Dot diagram for Nitrogen
Nitrogen has 5 valence e- write symbol Nput first 2 e- on rt sideAdd remaining e-’s CCW
The Octet Rule Noble gases unreactive (Ch 6) Octet Rule: noble gas configuration
8 outer level (stable) noble gas has 8 e-’s in outer level
(He has 2)
Metals lose e-’s to attain a noble gas configuration (NGC).
They make + ions (cations) Na 1s22s22p63s1 1 valence e- Na1+ 1s22s22p6 (NGC w/ 8
valence e-’s)
Scandium (21) e- configuration is: 1s22s22p63s23p64s23d1
lose 2e- (2+), or lose 3e- (3+)
Sc = Sc2+ Scandium (II) ion Scandium (III) ion
Sc = Sc3+
Sc
Silver (47) Predicted configuration is:
1s22s22p63s23p64s23d104p65s24d9
Actual configuration is: 1s22s22p63s23p64s23d104p65s14d10
Ag = Ag1+ (can’t lose any more, charges of 3+ or greater are uncommon)
Nonmetals gain e-’s to attain NGC
- ions (anions) S = 1s22s22p63s23p4 = 6 valence
e- S2- = 1s22s22p63s23p6 = 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… s2p6
8 valence e-’s (stable) octet rule
ArElectron 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. Ba2+ B. As3- C. Cu2+
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 -
NOTE: NO DOTS shown for cation
Ionic Bonding 0:38
dot & cross diagrams 2:57
Ionic Bonding
= Ca3P2Formula 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 pointsCoordination 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
TiO2
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) Ductility 2) Malleability
Due to the mobility of the valence electrons, metals have:
and
Notice that the ionic crystal breaks due to ion repulsion!
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 solidCompact & orderly patterns
1. Body-centered cubic: Fig. 7.14 Fig. 7.14 p.202: p.202:
every atom has 8 neighbors (except atoms on surface) Na, K, Fe, Cr, W
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