if you are not registered for che 361

If you are not registered for ChE 361

Please come see me

About Clicker Quizzes:

1) Review previous lectures

2) Review reading assignment

3) Assess understanding of today’s discussion

The Clicker Trials•Register your i>clicker by Monday, 27 January(Registration info posted on Canvas, click on link).

•You can take part in polling before registering, but scores will not be posted to Canvas until you register.

•If your i>clicker is already registered for another course, there is no need to register again.

•If you make a mistake registering, just re-register. i<clicker will accept the most recent registration.

Clicker Quizzes• You may consult with your neighbors, unless directed otherwise.

• You may consult with your text, but time is limited.

• Correct answer = 2 points Incorrect answer=1 point

• I drop the lowest 2 clicker grades to allow for absences/clicker problems/forgotten remotes.

1. Power on your clicker

i>clicker will power off after 90 minutes of inactivity.

i>clicker2 will power off after 5 minutes of inactivity.

2. When the polling begins, Press the letter corresponding to your answer.i>clicker–green light=answer accepted; flashing red=try again.

i>clicker2–a check mark ( √ )will show up beside your answer on LCD screen.

3. Ask if you need help

The Clicker Games-let’s try this!

Types of Bonding

• Ionic

• Covalent

• Metallic

• Van der Waals (Secondary)

The Periodic TableColumns: Similar Valence Structure

Adapted from Fig. 2.6, Callister & Rethwisch 8e.

Electropositive elements:Readily give up electronsto become + ions.

Electronegative elements:Readily acquire electronsto become - ions.

giv

e u

p 1

e-

giv

e u

p 2

e-

giv

e u

p 3

e-

ine

rt g

ase

s

acc

ept

1e

-

acc

ept

2e

-

O

Se

Te

Po At

I

Br

He

Ne

Ar

Kr

Xe

Rn

F

ClS

Li Be

H

Na Mg

BaCs

RaFr

CaK Sc

SrRb Y

Some electron configurations are especially stable.(Think “noble gases”)

Rule #2: Stable Configurations

Example: Na, Cl

Opposites attract

Rule #1: Electrical Neutrality

1) Ionic Bonding

Atoms take/give electrons to neighbor– Often 1 metallic & 1 non-metallic (Elements from opposite sides of table)

2) Covalent bonding

Atoms Share Electrons

Example: H2O

2) Covalent bondingAdjacent atoms share

electrons to achieve stable e- configuration

Reality check

ionic covalent

Nature of the bond reported as:Percent ionic character

3) Metallic Bonding• Share electrons (“sea of

electrons”)

• Orbitals never completely filled:Electrons jump from atom to atom

Section 2.7

Secondary or Van der Waals

Bonding

Rule #3: Dipoles almost always

occur

4) Secondary (Van der Waals) bonding

• Weak compared to primary bonds

• Can significantly affect material properties

4) Secondary (Van der Waals) bonding

+Ioncore

–

–

Fluctuating induced dipole moments

–

Ion core

Before:

After:

Ion core

Ion core +

• Permanent Dipole BondsPermanent dipole moments in the molecule.Bonds stronger than for Fluctuating

• Example: H2O

OHH +– O

HH +– O

HH +–

4) Secondary (Van der Waals) bonding

For which will VdW forces have the strongest influence on properties?Covalent bond: Where a rod meets a ball

A.Graphite(Carbon)

B.Diamond(Carbon)

Sections 3.1–3.4; 3.7

Structure of Crystalline

Solids

Cubic xl Structures

Unit Cell

• Smallest structural unit that generates a 3-D xl (if repeated).

• 7 Crystal Systems—Only 7 unit cell shapes for all xl structures.

Table 3.2Crystal Systems

Table 3.2, cont’d

Crystal Systems, cont’d

Unit cell

Cubic Systema = b = c

º

Fig. 3.4

Atomic Packing Factor

APF = volume of atoms in unit cell

total volume of unit cell

Metallic xl Structures

1) Face-Centered Cubic (FCC)

2) Body-Centered Cubic (BCC)

3) Hexagonal Close-Packed (HCP)

FCCAtoms at 8 corners & 6 faces

Equivalent of ? whole atoms.

Atomic Packing Factor (APF)= .74

Fig. 3.1

FCC Cubic structure

STM of PlatinumDept. Kings.edu/chemlab, Property of IBM

A scanning tunneling microscope (STM) is an instrument for imaging surfaces at the atomic level.

What’s an STM image?

Atoms….

You are under our control!

• 1990: IBM scientist Don Eigler used an STM to move single xenon atoms on a nickel surface

•The engineers moved 35 atoms to spell out "IBM" in a 10 micrometer logo.

FCC examples

Lab-grown copper (SEM)0.3 mm

Etched Aluminum (SEM)

GoldGalena (Pb ore)

A scanning electron microscope (SEM) produces images by scanning a sample with a focused beam of electrons. Yields topography and composition.

What’s an SEM image?

BCC

Atoms at 8 corners & 1 in center of

cube

Equivalent of ? whole atoms

APF = .68Fig. 3.2

BCC Cubic structure

STM of Aluminum (100) surface

https://wiki.fysik.dtu.dk/dacapo/Examples

BCC examples

Molybdenum Iron

Metallic xl Structures

1) Face-Centered Cubic (FCC)Cu, Al, Ag, Au, Pb, Ni, Pt

2) Body-Centered Cubic (BCC)Na, Fe, Cr, Mo, W

3) Hexagonal Close-Packed (HCP)Ti, Zn, Cd, Co, Mg

HexagonalSystem

a1 = a2 = a3 ≠ z

º

º

Fig. 3.7

HCP

Atoms at 12 corners, 3 in interior, 2 centered on basal planes

Equivalent of ? whole atoms

(APF)= .74Fig. 3.3

Hexagonal structure

STM of Nickel surface structure.

Dept. Kings.edu/chemlab, Property of IBM

Zinc hand sample

Hexagonal structure

SEM of Fine Cadmium powder

http://www.sciencephoto.com/media/8998/enlarge

SEM of ZnO nanowireshttp://www.lac.tu-clausthal.de/en/arbeitsgruppen/angewandte-photonik-

lac/projekte/zinc-oxide-nanowires-for-photonic-applications/

Hexagonal structure

HCP Examples

Titanium crystals

Cadmium crystal bar

Magnesium (SEM)

Atomic Packing Factors

BCC = 0.68 FCC = 0.74 HCP = 0.74