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6.5. Molecular Geometry. 6.5 NOTES. The properties (solubility, state at room temperature, etc.) of a molecule depend on two things :. 6.5 NOTES. The properties of a molecule depend on two things: The type(s) of atoms involved. The shape of the molecule. 6.5 NOTES.

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6 5

6.5

Molecular Geometry


6 5 notes

6.5 NOTES

The properties (solubility, state at room temperature, etc.) of a molecule depend on two things:


6 5 notes1

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved.

  • The shape of the molecule.


6 5 notes2

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved.

  • The shape of the molecule.

    What is VSEPR?


6 5 notes3

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved.

  • The shape of the molecule.

    Valence Shell Electron Pair Repulsion = VSEPR


6 5 notes4

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved.

  • The shape of the molecule.

    Valence Shell Electron Pair Repulsion = VSEPR

    Valence electron pairs tend to orient themselves as far apart from each other as possible.

    This applies to bonded and unbonded pairs, however, unbonded pairs tend to have more of an affect than bonded pairs. Why?


6 5 notes5

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved.

  • The shape of the molecule.

    Valence Shell Electron Pair Repulsion = VSEPR

    Valence electron pairs tend to orient themselves as far apart from each other as possible.

    This applies to bonded and unbonded pairs, however, unbonded pairs tend to have more of an affect than bonded pairs.

    Unbonded pairs are held closer in to the molecule, so they exert more influence on the shape of the molecule.


6 5 notes6

6.5 NOTES

The properties of a molecule depend on two things:

  • The type(s) of atoms involved (polar or nonpolar bonds).

  • The shape of the molecule.

    Valence Shell Electron Pair Repulsion = VSEPR

    A = central atom

    B = other atoms bonded to the central atom

    E = unbonded electron pairs on the central atom


6 5 notes7

6.5 NOTES

LOOKING AT THE SHAPES:

  • http://phet.colorado.edu/en/simulation/molecule-shapes


6 5

is a bonded atom

is the center atom

are unbonded electrons

Remember:

unbonded electrons exert much more influence on the shape of the molecule


6 5 notes8

6.5 NOTES

p. 200 – Memorize name, shape, and type of molecule


6 5 notes9

6.5 NOTES

Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule. If an “s” electron pairs with a “p” electron, it is called an “sp” orbital. P. 203


6 5 notes10

6.5 NOTES

Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule.


6 5 notes11

6.5 NOTES

Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule.


6 5 notes12

6.5 NOTES

Hybridization explains exactly where the electrons are positioned. (s, px,py,pz, etc.) It helps account for the electrons being spread around the entire molecule.

If an “s” electron pairs with a “p” electron, it is called an “sp” orbital. p. 203

In CH4 the s and p orbitals actually form “sp” hybrid orbitals for the electrons to occupy.


6 5 notes13

6.5 NOTES

In double bonds, the electrons repel each other so they spread out the bond area.

A sigma (σ) bond is between the nuclei of the two atoms.

A pi (π) bond is above and below the sigma bond.


6 5 notes14

6.5 NOTES

Let’s determine some molecules shapes and polarity:

OF2


6 5 notes15

6.5 NOTES

Let’s determine some molecules shapes and polarity:

CO2


6 5 notes16

6.5 NOTES

Let’s determine some molecules shapes and polarity:

HCN


6 5 notes17

6.5 NOTES

Let’s determine some molecules shapes and polarity:

CH4


6 5 notes18

6.5 NOTES

Let’s determine some molecules shapes and polarity:

NH3


6 5 notes19

6.5 NOTES

Let’s determine some molecules shapes and polarity:

BCl3 (B is an exception, because of its size it can only accommodate 6 electrons to be stable)


6 5 notes20

6.5 NOTES

Let’s determine some molecules shapes and polarity:

SO2


6 5 notes21

6.5 NOTES

What is the shape of these polyatomic ions?

NO31-


6 5 notes22

6.5 NOTES

What is the shape of these polyatomic ions?

NH41+


6 5 notes23

6.5 NOTES

So why is a molecule’s shape and the type of bonds it contains important?


6 5 notes24

6.5 NOTES

So why is a molecule’s shape and the type of bonds it contains important?

That is what will determine:

  • the state of matter for the molecule

  • the melting and boiling points

  • the ability to dissolve in water


6 5 notes25

6.5 NOTES

What are intermolecular forces?


6 5 notes26

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

Also called van der Waals forces

They are weaker than intramolecular forces (covalent

bonds).


6 5 notes27

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

What are the 3 types?


6 5 notes28

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

3 types

  • London dispersion forces (p. 207)

    weakest

    occurs between 2 nonpolarmolecules


6 5 notes29

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

3 types

  • London dispersion forces (p. 207)

    weakest

    occurs between 2 nonpolarmolecules

    occurs for a short time when the electrons, which are constantly moving in a molecule, are not completely balanced (one side is temporarily negative and the other side is temporarily positive).

    this temporary charge then induces another molecule to have a temporary positive or negative end.


6 5 notes30

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

3 types

  • London dispersion forces (p. 207)

    weakest

    occurs between 2 nonpolar molecules (usually large molecules)

    occurs for a short time when the electrons, which are constantly moving in a molecule are not completely balanced (one side is temporarily negative and the other side is temporarily positive).

    this temporary charge then induces another molecule to have a temporary positive or negative end.

    also called induced dipole


6 5 notes31

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

3 types

  • London dispersion forces

  • Hydrogen bonding (p. 206)

    the next strongest of the forces

    The hydrogen atom of one molecule is attracted to the nitrogen, oxygen, or fluorine in another molecule.

    All the atoms have to be in polar bonds.


6 5 notes32

6.5 NOTES

Intermolecular forces exist between one molecule and another molecule.

3 types

  • London dispersion forces

  • Hydrogen bonding

  • Dipole-dipole forces (p. 205-206)

    strongest of the intermolecular forces

    Occurs between two polar molecules

    Partial positive end of one is attracted

    to partial negative end of another.


6 5

A technician was cleaning up the laboratory

when he discovered two steel gas cylinders.

Puzzled as to what was inside, the

technician took the cylinders to his supervisor.


6 5

A technician was cleaning up the laboratory

when he discovered two steel gas cylinders.

Puzzled as to what was inside, the

technician took the cylinders to his supervisor.

“One contains gaseous F2 and the other Cl2,

said his supervisor.

“But which is which?” asked the technician.

The supervisor responded indignantly, that

to a chemist, the answer should be obvious.


6 5

A technician was cleaning up the laboratory

when he discovered two steel gas cylinders.

Puzzled as to what was inside, the

technician took the cylinders to his supervisor.

“One contains gaseous F2 and the other Cl2,

said his supervisor.

“But which is which?” asked the technician.

The supervisor responded indignantly, that

to a chemist, the answer should be obvious.

Which tank is which?


6 5

  • HINTS:

  • Which intermolecular force is present in

  • these tanks?


6 5

  • HINTS:

  • Which intermolecular force is present in

  • these tanks?

  • How would molecule size affect this

  • force?


6 5

  • HINTS:

  • Which intermolecular force is present in

  • these tanks?

  • How would molecule size affect this

  • force?

  • Do stronger forces result in a higher or

  • lower boiling point?


6 5

  • HINTS:

  • Which intermolecular force is present in

  • these tanks?

  • How would molecule size affect this

  • force?

  • Do stronger forces result in a higher or

  • lower boiling point?

  • Which substance has the stronger

  • intermolecular forces?


6 5

Which tank contains

which gas?


Chapter 6 test

CHAPTER 6 TEST

  • 25 multiple choice (3 points each)

  • 5 drawing molecules (5 points each)

  • 1 extra credit (3 points)


Chapter 6 test1

CHAPTER 6 TEST

  • 3 types of bonding

  • Covalent

  • Ionic

  • Metallic

  • Chart p. 176

  • 0 – 0.4 = nonpolar covalent

  • 0.5 – 1.9 = polar covalent

  • 2.0 and above = ionic

  • Properties of ionic and covalent compounds

  • Bond length vs bond energy

  • Octet rule (there are exceptions – B, Be, H, S, and P are the common ones)


Chapter 6 test2

CHAPTER 6 TEST

  • Electron dot notation for atoms and ions

  • Lewis structures for covalent compounds

  • Resonance structures

  • Lattice energy

  • Polyatomic ions – how to draw them (remember to add or subtract e-)

  • Using VSEPR to determine shapes

  • Chart p. 200

  • Intermolecular forces

  • London Dispersion forces

  • Hydrogen bonding

  • Dipole-dipole bonding

  • Hybridization


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