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Bonding Introduction. Octet rule Types of bonds Lewis structures Geometry. Video 5.1. Types of Bonds. Octet Rule Review. Atoms bond with other atoms by sharing or transferring electrons in order to achieve a stable octet (8 valence electrons). Bonding creates stability!

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Bonding Introduction

Octet rule

Types of bonds

Lewis structures

Geometry


Video 5.1

Types of Bonds


Octet Rule Review

Atoms bond with other atoms by sharing or transferring electrons in order to achieve a stableoctet(8 valence electrons). Bonding creates stability!

*When bonds are formed energy is ___________.

*When bonds are broken energy is ___________.

released

absorbed


Ionic Bonds

  • Transfer of electrons from the cation to the anion (metal to nonmetal).

  • High melting point and boiling point

  • Mostly hardcrystalline solids

  • Conduct as liquid (either melted or dissolved) due to mobile ions.


Ionic Bonds

Sodium Chloride: NaCl (table salt) properties:

  • Hard

  • Solid crystals

  • High melting point, forget boiling!

  • Liquid phase conducts (electrolytes are salts)


Metallic Bonds

  • Metals only

  • All metals lose their valence electrons and form a sea of electrons

  • High melting point and boiling point

  • Insoluble in water

  • Always able to conduct heat and electric due to mobile electrons

  • Malleable

  • Ductile


Metallic Bonds

Copper (Cu) properties:

  • Hard solid

  • High melting point, forget boiling!

  • Malleable and ductile

  • Conductor

  • Can’t dissolve


Metallic BondsSea of electrons

Copper (I) ions Copper (II) ions


Covalent Bonds (Molecular)

  • Nonmetals only

  • Share electrons between atoms

  • Low melting point and boiling point

  • Never conduct heat or electricity

  • Soft solid or gas


Covalent Bonds

Dextrose C6H12O6 (Sugar) properties:

  • Soft

  • Melts easily in sauce pans for caramel

  • Doesn’t conduct (nonelectrolyte)


What type of bond is created?

M+ NM = Ionic

  • Ca + O

  • K + Br

  • S + Cl

  • I + S

  • Li + Mg

  • Ba + S

M + NM = Ionic

NM + NM = Covalent

NM + NM = Covalent

M + M = Metallic

M + NM = Ionic


Video 5.2

Ionic Compounds


Review: Find the ionic formula:

-

KBr

+

  • K + Br

  • Mg + Cl

  • Na + S

  • Ca + S

+2

-

MgCl2

+

Na2S

-2

CaS

+2

-2


Draw Lewis structures:

KBr

MgCl2

Na2S

CaS


Which subatomic particle is involved in bonding?

Electrons only!


Geometry of ionic crystals

Ionic crystal

Ions


Video 5.3

Covalent Compounds


Covalent Lewis Structures Rules: CCl4

C: 4 + 4Cl: 7 = 32 valence e-

  • Add up all valence e-

  • Draw a skeletal structure with bonds between elements. Least frequent element in the middle.

  • Subtract 2e- from total for each bond drawn.

  • Draw in remaining e- to fill each atom’s octet.

  • Evaluate: each atom should have 8 e- only.

Cl

Cl—C—Cl

Cl

32-8=24


VSEPR

“Valence shell electron pair repulsion” is a model for molecules. Lone electron pairs are repelled by one another and should be placed as far apart as possible.


Geometry

  • Linear: The molecule is on one plane (flat) such as CO2 or H2.

  • Bent: The molecule is bent at angle like H2O due to unshared electrons and two bonding pairs on the central atom.


Geometry

  • Pyramidal: The molecule has a triangular shape like NH3 due to a lone pair and three bonding pairs on the central atom.

  • Tetrahedral: The molecule has four

    bonding pairs and no lone pairs on

    the central atom like CH4.


Examples:

  • Draw the following molecules and identify their geometry:

  • PCl3

  • SiCl2H2

  • Br2

  • H2S

pyramidal

tetrahedral

linear

bent


Video 5.4

Bond Polarity


Bond Polarity

The earth has two poles; North and South.

A magnet also has two poles.

Bonds may have two poles. This means one element is charged different than the other.

If a bond is polar, the two elements have different electronegativities. The element with a higher electronegativity will be more negative.


Bond Polarity


Bond Polarity


Nonpolar Bond


Bond Polarity


Ionic, polar or nonpolar?

P

P

  • C-Br

  • Na-S

  • C-C

  • H-O

  • K-O

  • Be-B

  • As-O

  • N-O

  • C-O

  • F-F

  • S-C

  • N-H

P

I

P

NP

NP

P

I

NP

I

P


CovalentBonding

  • If 2 atoms or more form a bond with the same electronegativity the bonds are nonpolar and they share e- equally. ( F-F )

  • If there is an electronegativity difference between bonded atoms, the bonds are polar and e- are pulled toward the more electronegative atom. (H-F)

  • If a bond is polar, the molecule will have a slightly negative and slightly positive side, like 2 poles of a magnet.


Video 5.5

Molecular Polarity


Molecular Polarity

  • A polar molecule will be asymmetrical.

  • A nonpolar molecule will have a symmetrical shape or all nonpolar bonds.


Molecular Polarity

Which are polar molecules? Show charges.

NP

+

+

P

P

+

+

-

-

-

NP

NP

-

+

-

-

-

-

+

-


Molecular Polarity

Water is polar, and like dissolves like, so only polar molecules are soluble in water. Polar molecules are also attracted to an electric field.


Molecular Polarity

  • As you can see, normally polar molecules are unaligned.

  • When a electric source comes by, the molecules quickly align themselves.


Video 5.6

IMF


IMF

  • Intramolecular forces is another name for bonds, that keep elements together in compounds.

  • Intermolecularforces of attraction are weaker than bonds, but are responsible for holding a substance together (multiple molecules in a confined area).


IMF

  • The stronger the IMF, the tighter the structure (solid). The melting and boiling points will be high.

  • The weaker the IMF, the looser the structure (gas). The melting and boiling points will be low.


Dipole-Dipole

  • Dipole-Dipole attractions are strong forces betweenpolarmolecules. It is like static holding the + and – charges together.


Hydrogen Bonding

A special case: Hydrogen Bonds are the strongestbonds between Hydrogen and very electronegative atoms such as F, O and N. (H bonds are FON!) For example, H2O and HF, due to their polarity, they will attract each other.


London Dispersion Forces (LDF)

The weakest attraction betweennonpolarmolecules occur because electrons temporarily shift creating a temporary + and – charge. The more electrons the compound has, the stronger the force is.


Summary

  • From weak to strong:

    • Nonpolar LDF

    • Polar Dipole Dipole forces

    • Hydrogen bonds

    • Covalent Bonds

    • Ionic Bonds

    • Metallic Bonds


Class Notes


Show the individual and bonded Lewis structures:

  • Li and F

  • Mg and O

  • Be and S

  • What did all the cations do?

  • What did all the anions do?

  • Which of the subatomic particles were changed and how were they changed?


Type of Bonding?

  • CaCl2

  • CO2

  • H2O

  • BaSO4

  • K2O

  • NaF

  • Na2CO3

  • CH4

  • SO3

  • LiBr

  • MgO

  • NH4Cl

  • HCl

  • KI

  • NaOH

  • NO2

  • AlPO4

  • FeCl3

  • P2O5

  • N2O3


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