Sparks

CH301

WHY IS EVERYTHING SO

DIFFERENT? Gas, Liquid or Solid?

UNIT 3 Day 6

What are we going to learn today?

MO of large molecules

Recognize different molecules have different

physical properties

Classify Intermolecular Forces

Most molecules have

A. An even number of electrons

B. An odd number of electrons

C. Equal chance of even or odd

POLL: CLICKER QUESTION

Most molecules are

A. diamagnetic

B. paramagnetic

C. Evenly split between the two

POLL: CLICKER QUESTION

How is this tool used..

Calculate the lowest

energy geometry;

Where is the electron

density

What if it is a complicated molecule with lots of atoms

It is hard to relate the MO to AO

None the less the MOs are useful

Other way we use MO, just the pi electrons

VB for sigma bonds

MO for the pi bond

Where are the electrons?

Delocalized around the molecule

Typical MO for organic molecule

Almost always diamagnetic

HOMO/LUMO

Energy gap

Light absorption

Dyes – homo lumo gap is

the color that is

absorbed, gaps as a

function of structure

MO picture of Ethanol

VSEPR and VB to get visual image

Predict Polar just from ball and stick

Chemical Composition & Shape

Physical Properties?

GAS? or LIQUID?

Types of Forces

Intramolecular Forces: forces that hold together an individual molecule

Types of Forces

Intermolecular Forces: forces between

different molecules

e.g., forces between:

separate CO2 molecules in CO2

separate H2O molecules in H2O

Thought Question!

H2O(g) + 927 kJ 2H(g) + O(g)

H2O(l) + 40.7 kJ H2O(g)

For water, which are stronger:

A.The intermolecular forces.

B.The intramolecular forces.

What dominates the interaction in

condensed phases?

What are these forces?

Classify forces.

Define IMF.

REMEMBER TAPE

REMEMBER CHARGED ROD and LIQUIDS

INTERMOLECULAR FORCES

DOMINATE FORCE IN CHEMISTRY – COULOMBIC

INTERMOLECULAR FORCES

DOMINATE FORCE IN CHEMISTRY – COULOMBIC

Qualify the word “intermolecular”

Boling Point: 1413 °C

INTERMOLECULAR FORCES

CONDENSED PHASE – BUT NOT IONIC

MOLECULAR CONDENSDED PHASE:

MOLECULAR LIQUID OR MOLECULAR SOLIDS

“PARTICLE IS A MOLECULE”

Intermolecular forces are

based on attraction of

opposite charges.

Electrostatic forces

In covalent molecules,

intermolecular forces are

based on the molecule

polarity.

REMEMBER:

A molecule which is polar overall will have a NET

DIPOLE.

From now on we refer to this type of molecule as a

DIPOLE.

INTERMOLECULAR FORCES: dipole-dipole

Attractive force between

partial negative end of

one molecule and

partial positive end of

another molecule.

Strength depends on

distance and dipole

moment.

E 1

r3

POLL: CLICKER QUESTION

CLICKER QUESTION

ALL NONPOLAR COMPOUNDS ARE GASES:

A) TRUE

B) FALSE

Important Information

LM23 posted

Extra, non-graded practice:

Laude LM Lecture 16 & 17