HOW THE WORLD WORKS,ACCORDING TO CHEMISTRY

Part 8a

Part 8a

Molecular Shape

THE MODEL WE WILL USE TO DETERMINE MOLECULAR

SHAPE IS CALLED _________

(V_________ S_________

E__________ P________

R_______________)

THE ELECTRON PAIRS AROUND THE ____________ ATOM OF A MOLECULARCOMPOUND REPEL EACH OTHER, ANDTRY TO GET

THIS DETERMINES THE SHAPE OF THE MOLECULE

I HATEYOU!!

GET AWAYFROM ME!!!

CENTRAL ATOM

PERIPHERALATOM

PERIPHERALATOMELECTRONS

ON CENTRALATOM

ELECTRONSON CENTRALATOM

VSEPR STEPS 1 and 2

1. Draw the _____________________

2. Count the ____________________

_______________________________What molecular shape gets the

electrons as far from each other as possible?

Step 1 and Step 2:

BeH2

Note: compounds of beryllium (Be) are often exceptions to the Octet Rule.

Beryllium may have only ____________ electrons pairs around it.

The pairs of electrons around the central atom are referred to as

Think of these as balloons. What shape allows the “balloons” to get as far from each other as possible?

For 2 electron clouds around the central atom… The moleculargeometry is

The bond angle is

Compounds of BORON (B) are also often exceptions to the Octet Rule.

H B H

H

Step 1 and Step 2: BH3

They often have ______ electron clouds around the central boron.

For 3 electron clouds around the central atom, (no unshared pairs on the central atom)…

The moleculargeometry is

The bond angle is

METHANE GAS (CH4) is natural gas

Step 1 and Step 2

When there are ______ electron clouds around the central atom (none of which

are unshared pairs), this shape is called

_______________________

Build a “ball and stick” model of methane.

WHITE – HYDROGEN

BLACK – CARBONSINGLE BOND:

To draw a more 3-D Lewis structure: This shape of bond, indicates that the atom is sticking forward. This shape of bond, indicates that the atom is sticking back.

UNSHARED PAIRS ON THE CENTRAL ATOM

Unshared pairs occupy a position in space, so any unshared pairs

_______________________________ are included in the pairs of electrons that affect the shape.

AMMONIA (NH3)

Step 1 and Step 2

NH3: around the central atom, there are ____ electron clouds

However, ____ of those clouds is an unshared pair, so the molecular geometry is called:

_______________________________

Build a model of NH3

BLUE - NITROGEN

Draw the Lewis structure with the 3-D bonds.

WATER

Step 1 and Step 2

For H2O: Around the central atom,

there are ______ electron clouds

However, ______ of those clouds are unshared pairs, so the molecular

geometry is called_______________

Build a water molecule…

RED - OXYGEN

Draw the Lewis structure of water with 3-D Bonds.Whenever you have only 3 atoms,

they must ______________________

_______________________________

so the bonds you draw ___________

_______________________________

When drawing a linear molecule, you

ALWAYS SOMETIMES NEVER

use 3-D bonds.

Unshared pairs on the central atomtake up more room than shared pairs because….

Which one of the molecules below has an unshared pair on the central

atom? How do you know?

Double Or Triple Bonds On The Central Atom

count as a

____________________________

in molecular geometry

SULFUR DIOXIDE SO2

Step 1 and Step 2

SO2 : Around the central atom, there are _____ electron clouds

However, _____ of those clouds is an unshared pair, so the molecular geometry is

called_______________

Build a model for

SO2

normally… sulfur is red – like oxygen. However, because it has more than 2 bonds to it, you must use a black atom.

For a double bond -

MORE THAN ONE CENTRAL ATOM

Molecules may have more than one central atom. A central atom is an atom that is

_____________________________________ within a compound. When there is more than one central atom in a molecules, you must determine the shape around

_____________________________________

ETHANOL -C2H5OH

Build an ethanol molecule.

CARBON #1M. G. ____________________

CARBON #2M. G. ____________________

OXYGENM. G. ____________________

Our next step will be:

8b

POLARITY