Chapter 8

Chapter 8Chemical BondingChemical Bond: __________________________ ________________________________________________________________________________

The type of bonding is determined by the way the valence e-s are redistributed.

Molecular or Covalent BondingMolecule: ______________ ______________________________________________e.g. H2O

Diatomic Molecule: molecules containing __________ atoms.E.g. O2 , CO , HF, NO

More definitions

Octet Rule: where chemical compounds tend to form, such that ______________________________ _________________________________________This is done by _______________________________ (becoming an ion or entering a covalent bond)e.g. Fluorine gas exists as F2 . F - F

Each F atom has achieved a stable octet by _______________of electrons.

(do the same with:O2 , PF3 )

e.g. HCl Chlorine has a stable octet, but H does not.Thats because there are _____________________________________________________________________i.e. __________________

How many electrons would it need to fill an octet?Is that possible?

Bonding

When atoms bond they ______________ _________________In dot notation this is represented as two dots between symbols, one from each atom

(Do F2 , PF3 , HCl )The unshared pairs of electrons are also known as ________________.The _________________________________________.(do F2 , & PF3 )

These representations are known as:Lewis Structures: _____________________________ ________________________________________________________________________________________The dots representing the lone pairs can also be dropped. The new representation is known as ____________ ____________________

A single shared pair is known as a _____________. Lets consider O2 :(Diagram)

The sharing of ____________________ between 2 atoms is known as a ________________.

Lets consider N2 :(Diagram)

The sharing of ____________________ between 2 atoms is known as a ________________

Double & Triple Bonds are also known as:Multiple Bonds.

We still havent explained why carbon can form 4 bonds instead of 2___________________Lets look at Carbon (6):(ec, orbital diag., Lewis, & Structural)

It makes sense to assume that Carbon forms 2 covalent bonds.

But when Carbon bonds with other atoms, a special thing happens.The 2s & 2p merge together to form an _____________. Now apply Hunds rule.(Diagram)

So now, Carbon has 4 single bonds.Hybridization also applies to Be, B, & Si.

Lets review with some examples:(Central atom is the least EN atom or C)(e.gs of NH3 , HCN , C2H6 , C2H4 , C2H2)Show Lewis structureTwo Types of BondsIonic: results from 1 atom giving up its valence e-s (cation) & transferring them to another atom (anion)e.g. NaCl

Covalent: _____________________ ______________________________Most bonds are between these extremes!

Non-Polar Covalent

Non-Polar Covalent: the bonding valence e-s are ________________by the atoms resulting in _____________________of electrical charge. e.g. N2

Polar covalent bond

Polar Covalent: the bonding valence e-s are more strongly attracted to the more EN atom resulting in an ___________________________________. It is still sharing, not a transfer like in ionic. e.g. CO2

So: Chemical Bonding

IonicCovalent

Polar Non-Polar

The type of bonding can be determined simply by the _____________________ ______________________________(EN) of the 2 atoms. 6.2 p 177.

E.g.s:A H-F molecule has an EN difference of:4.0 (for F) 2.1 (for H) =For Na-Cl the EN difference is:3.0 (for Cl) 0.9 (for Na) =For H-H (H2) the EN difference is:2.1 (for H) 2.1 (for H) =

The difference tells you what type of bonding that is occurring:> 1.7=Ionic< 0.3=Non-Polar Covalent0.31.7=Polar Covalentor:EN difference = 00.31.73.3I--------I--------------------I---------------------------Inon-PolarIonic Polar(see p.162 Fig.6-2 )Going back to the previous examples:

H-FEN = 1.9Na-ClEN = 2.1 H-HEN = 0

Other examples:Mg-SCO2 Intermolecular Forces:-forces ______________ molecules.-weaker than ionic & covalent bonds.In Polar Covalent (EN=0.3-1.7)The EN difference creates a ____________ __________________________________________________e.g.I-Cl=>I---Cl=>ICl (2.5) (3.0)+-0.5 Difference Dipole

Dipole-Dipole interactionIntermolecular force __________________________________________________________________

Strong intermolecular force.

Hydrogen Bonding

The ______________________ force that has H partially bonded to an electronegative atom. E.gs:Causes higher than normal boiling points water is a liquid instead of a gas @ room temp.__________________________________________________________e.g. H2O , HCl , HF , H2S (do diagrams)I love water!!! (why?)Non-Polar Molecules (EN= 0 - 0.3)There is no dipole because the EN diff is too low. But a ____________________________________________________________________________________________, which effects the next molecule, and so on.e.g. Draw Cl2 gas with London dispersion, aka Van der Waals forces.Other e.gs? O2 , H2 , F2 London Dispersion forces

Average shapeTemporary shiftEffects other molecules