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)

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

Ca2+

NO DOTS shown for cation

This is named the “calcium ion”.“calcium ion”.

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)

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 = 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+

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 Clmetal (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)

Ca P

combining calcium and phosphorus:

Ca P

Ca2+ P

Ionic Bonding

Ca2+ P

Ca

Ionic Bonding

Ca2+ P 3-

Ca

Ionic Bonding

Ca2+ P 3-

Ca P

Ionic Bonding

Ca2+ P 3-

Ca2+ P

Ionic Bonding

Ca2+ P 3-

Ca2+ P

Ca

Ionic Bonding

Ca2+ P 3-

Ca2+ P 3-

Ca2+

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

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) Ductility 2) 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

+ - + -+- +-

+ - + -+- +-

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 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

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”